Why there is not as much as voting to questions and answers as in other stack exchange sites like overflow or information security? Why users do not cast their votes even its simple?
Stack Overflow has 5.4 million users, Information security has 81000 users. Chemistry has a meagre 16000. These are just the plain registered users numbers.
From the site analytics I know that there are about 100 users (average) that take action every day. There are about 1000 votes cast every week.
We are a small community, and yes, voting could be more. But it is completely normal behaviour for the site. There is nothing to worry about. Additionally, voting has been increasing (in average) for the past two (or three) years now (with an anomaly around the graduation of the site). The trend is upwards, that is good.
But just in case you did not know already: Vote Vote Vote Vote Vote Vote Vote!