In my opinion, that's only a fashion.
Writing a few words does the same, essentially.
Probably creates more of an impression and tends to encourage discussion, too; nobody really goes back to look at a thumbs-up count and it's much more of a social media thing (and IMHO more about "engagement" i.e. cynically encouraging telemetry for ads and stuff than it is about actual interaction).
But not the thing with quoting someone else's post in its entirety just to add +1 at the end, which is annoying, not least when the majority of posts are various people doing the same. Fortunately it's a bit passé now. And also not making the same point over and over in multiple topics, which also undermines whatever point is being made: it's very easy for it to simply be perceived as "this again?!
" and to switch off.