Let’s see how many bad reasons for this I can come up with in 30 seconds:
1. Social media may be popular but it is not universal (I still know people without a Facebook profile for instance). Thus, while the government should expect that someone may truthfully answer “I don’t have social media accounts”, I’ll bet money that anyone actually giving that answer on their visa application is screwed.
2. Huge numbers of social media profiles are completely FAKE. Combined with #1 above, if you don’t actually use a particular site but it seems like you do, you are again screwed.
3. Some people have extremely common names and legitimately do not want their pictures posted. Therefore, it is likely there are hundreds of real accounts with your name, many even in your city, that are not you. If the government is trying to determine if you “lied” about having an account, how many of these are they going to accuse you of owning? Or are they just going to conclude, based on the stuff being posted by those people, that your application should be denied?
4. The government does not run these sites, corporations do (and ultimately, random employees made some rules for running them). Suppose #2 above occurs, and someone is posting insane stuff as “you”; great, now your entire damned visa application is in danger, and some random set of rules made up by an employee at Facebook or Twitter is going to decide your fate. Can you get the profile taken down? Ask Facebook. Can you “prove” the profile is not you? Follow random rules from Facebook. And so on.
5. Not everything I do is on social media. And if I were to set up a secret club or criminal enterprise, do you think I’d be writing about it on Twitter and Facebook?!?!? What will exist on social media for a lot of people is an endless firehose of crap, which will mostly give the government way too much information to sift through. It will be a huge waste of time.
In other words, this policy can definitely hurt legitimate applicants and is not likely to add any useful information when screening applicants that “should” be denied.