I mine because I already have a gaming pc that can do a bit of mining. It gave me my first Bitcoin and still gives me around 40-50$ a month at current price. So in my mind depends on the case.

If you only have to spend the money to pay for the extra electricity and you mine sure things and easy (no research), like mining for Nicehash, it's really a good idea. If you want to risk mining new coins to try to get lucky getting many coins early at a super cheap price, it's more risky and requires a lot of research... Middle ground would be mining in a pool but mining safe coins...

=) Hope my 2 cents help.