This question might sound very stupid, but trust me, it's not. The fundamental reason for its ubiquity is surprising, even a bit embarrassing. Let’s first get into some background…

The "Like" button has not always been a standard in social media, as it is now. It was first introduced by a video sharing company called Vimeo, but to be honest, it has not a lot to do with the like button we have everywhere today.

The First true like button (Like button as we know it) was first introduced by Facebook in 2009, and it has an interesting story behind it.

At that time, Facebook wasn’t the Multi-Billion-dollar company it is now. There was just a small number of people working in the company then and they only had comments feature then and they observed that most Facebook posts had similar comments. Like, for example, Let’s take a guy named Tony and he posted a photo on Facebook that he got a job in Apple. Think for a second, what the comments for that post would be - and there is no like button…

It will probably look something like this...

Congratulations…. Congratulations… Congratulations…. Congratulations…. Congratulations.

So, the smart guys at Facebook wanted to remove this redundancy- because it was unnecessary and the internet wasn’t as fast or as powerful as it is now. So, they wanted to come up with a shortcut. As you know, the guys at Facebook are going to be smart, they prototyped the button in a matter of hours. The conundrum here was naming it and giving it a symbol. So, the project stayed frozen for months. A lot of ideas were discussed, like naming it “Awesome button” and a variety of different symbols like “star”, “plus” and the “thumbs up”.

Finally, it was up to Mark Zuckerberg to decide the symbol and name. As we all know now, it was named the "Like button" and given the Thumbs up symbol. It was an instant success. Soon appeared on YouTube, Google Plus, Instagram, blogs, and all many other smaller social media sites which do not exist now.

If you think about it, I have not yet answered the question in the title… To understand that, Think about, why you post a photo on Instagram? What every “like” for your Instagram post means to you?  What did you feel when someone has liked your photo?

The successes of the like button are because of the same reason as the successes of Social Media in general.

The common answer one would give if they are asked “why are you posting your personal photos on Instagram?” is that “I am expressing myself”, At least, that’s the answer I got.  But I think it is a total sham.

What I think the real reason is…  people need approval. In this context don’t take the word approval in a literal sense, but think in a connotative and figurative way; like, when you are trying to cook, you expect the folks who eat it to say” its tasty!!”. Most of the people are not indifferent to approval or disapproval, even though they may claim the contrary. And it is the real reason people post photos on social media if they don’t care, why bother posting…

The comments section is a hassle, you need to expend some effort to express approval, which not a lot of people will bother doing and so, the approval or the disapproval one gets is usually lesser too. Since approval – the reward of posting photos on social media – was lesser, the number of photos posted overall was lesser too. Like button simply reduced the friction; click of a single button, you can express your approval. So, Since the rewards for posting a photo is higher, the number of photos posted also increased greatly. So, it is a task made simpler for both people posting the photos and the ones expressing the approval (or disapproval). A win-win situation for both us and Facebook.

There is also another significance to the like button. I don’t think it is a widely spoken thing now as it was some years ago, but it is something I am certain that everyone who posts a photo on Facebook or Instagram thinks about. "How many likes my photo got?".I don’t know about you but, In my school days, I witnessed a lot of guys talk often about the number of likes one’s photo got on Facebook. It’s not a trivial thing as you may think at first glance. A number which doesn’t even mean anything almost treated as a signifier of Social Status (popularity and that sort of social status). Look at how powerful a single trivial data point became…

Ever wondered why Instagram hiding other user’s post’s number of likes?? The official statement from Mark Zuckerberg is “We want people to be less interested in how many likes a post gets, and focus more on connecting with other people.” But I don’t for one second believe Its intentions are as altruistic or benevolent as that, At least, there is an ulterior motive. The probable reason is that Facebook might have seen that people are deterred from posting more photos, seeing their friends getting more likes than them, so hiding the number from the users might motivate (at least not demotivate) them to post more photos. More the number of posts, the More average session duration, and the More the money Facebook makes.

And, above all, it gave a single objective data point for Facebook to base targeted advertising on instead of using natural language processing to get data from comments, which could be more precise, but the number of data points would be lesser- If you don’t know yet, Data is the most valuable asset for Facebook and that data makes Facebook, arguably, the most powerful company in the world. (I will talk more about it in another article)

Looking at things and my perceived tone, don’t judge me as a tech hater or anything, In fact, I am the exact opposite, I just appreciate great design and arguably, there is no greater or more powerful design than the “like button” in the modern digital world.

References

User Friendly by Cliff Kuang and Robert Fabricant

Awesome book about design, check it out 

https://www.amazon.in/User-Friendly-Hidden-Design-Changing-ebook/dp/B01HR5DVAQ