People understand the platform better, no need to lure famous people to the site, there are other ways to verify (e.g., link to twitter account on web page), many more people across the spectrum of "famous" so it's hard to button down who/what is famous enough for the checkmark, global audience means famous in one place != famous in another, no consistency in how verified actually works, verified accounts became Star-Bellied Sneetches, etc.
The verified system isn't about luring people to the site, it's about making sure certain accounts can't be impersonated.
The problem is that Twitter doesn't verify consistently, but it's is still an important feature, e.g. Imagine the mischief that could be caused if there was no way to tell which of several accounts was the real Donald Trump.
Except that you would know which account was the real Donald Trump, because Donald Trump would be on TV telling you so.
Extremely well-known figures have other ways to let you know which account is theirs. The harder set of people are the sort of low-to-medium famous. Or locally famous, not globally famous. The verified system has never worked well for that group anyway.
And yet every other week there's another news outlet publishing tweets from "Julian Assange" that aren't actually from Julian Assange (here's one from last week [0]), because twitter refuses to verify him and the people copying his account do it very well.
Now imagine that at the presidential level. No thanks.
