It seems to me that the level of voting on Physics SE is noticeably lower than on most other SE sites that I frequent and lower that it has been in the past (I have been a user on the site for several years). A casual look down the list of most recent questions shows that the vast majority are on only 0 or 1 vote. I remember a time when a question would get 1 or 2 up-votes, simply if it was constructive, valid and well-presented. In fact, I get the impression that, these days, the voting system is being used almost exclusively as a tool to 'punish' questions that are deemed unworthy.
If people aren't using the voting system, there are two potential issues I can see: firstly, there is a lack of reward/incentive for people to stick around and spend their time answering questions. Secondly, it will lead to a lack of differentiation between good/bad questions and answers - the good will get lost amidst the bad/mediocre.
So, what has happened with the voting? If people aren't using it, then it may as well not be there ...