Raise ATC from CO or button?

[Joost1982]

In some posts on this forum I read that some people "do not understand position enough". They get the advice to raise more from the CO and the button with crap hands (ATC). I have a couple of questions about this advice.

(1) Why do you have to raise?

Let's say you raise 4BB with ATC... then you risk 4BB to win 1,5BB. When the blinds fold 75% of the time, then you pick up 3x1,5=4,5BB - 1x4BB = 0,5BB profit. On the limits I play (25NL and sometimes 50NL) people in the blinds tend to call more than 40-50% of the time when you raise. Isn't this going to cost you more than you win then?

(2) What do you do when they "play back at you"?

When they just call and check to you on the flop, you cbet (when you hit nothing) and they call/raise, then it is the end of the hand, right? And when they preflop reraise, you check the odds, but then it is almost also the end of the hand?

I'm just wondering if this ATC raising is really profitable. Maybe I'm not getting it, but I really want to understand the game better, that's why I'm asking this (stupid) question...