In poker, nothing is ever done in a vacuum. All of our decisions consider a number of variables, which extend beyond the basic mechanics like the betting action and the cards you’re playing. These are “metagame” factors, and become more important when you’re playing against the same players all of the time.
They include things like history with an opponent, how you’re perceived at the table, how your actions could effect the dynamics between you and your opponent(s) and how this could affect long term profitability, etc.
For example, a betting line may be the correct play in a vacuum, but due to the meta-game considerations against certain opponents – taking a different line could be more profitable for you in the long term.
Poker is a mental game to a large degree, and you want to be able to beat your opponents on a psychological level. When considering the metagame in tournaments, you might want to play tight early on in the tournament to exploit your tight image later to steal pots when the blinds go up.