Well the main reason isn't controlling the temperature itself, I just assumed that by controlling voltage you could control temperature too.
Imagine situation: I'm soldering something and I want to take a 5 minute break. If I leave my iron on, it would consume a lot of electrical power and it may burn out (cheap soldering iron). But if I were to leave the iron off, after those 5min I'd have to wait a few minutes till iron gets hot again. Lowering voltage to about 60V would certainly take care of all problems.
Back to topic. I don't know why but dimmer switches at my local shop are very expensive (more than 15$). Basicly I'm just looking for a dimmer switch schematic, so I could save some money.