Tit-for-tat--meaning if you raise your price, I'll match you by raising mine, and if you lower your

Question:

Tit-for-tat--meaning if you raise your price, I'll match you by raising mine, and if you lower your price, I'll match you by lowering mine--seems to be a win/win strategy for both firms competing in a balanced oligopoly industry. So why does it not always end up as a win/win situation for them?