Sarcasm however, is my fuel for the day
[/sarcasm off]
There will always be a reason for people to post quick reply's. +1 in most cases is the short version of i agree. Now i agree on the fact that this lacks a further explanation about why the person in question agrees. This might be due to the fact some people aren't as straight forward in they're opinion, like the words the OP used, or haven't got anything to really add besides the fact that they agree on the subject.
Some people grow a bigger e-peen when they look at there postcount, some are just trying to get there opinion across in the short version.
Even when postcounts are removed, this will most likely still happen.