Earlier quoted context omitted.
Keeps the game fresh. If the game changes it gives people a reason to want to play again to figure out new combinations. Otherwise the meta gets set and it never changes and that gets old quickly.
Not necessarily. For instance rocket league was released in 2015 and hasn't gotten any such update since 2017. If the base is solid the players can spend their time mastering what they are given and over time it grows on you. Imagine chess buffing up the pawn and nerfing the bishop.
For games like Rocket League, CSGO, Overwatch, Apex, etc. The teams are even no matter what (skill aside). Meta still exists however, as anyone who has played multiple years of any of these games sees. Expected attacks, combos, and preferred approaches change over time as people discover weaknesses to the existing metagame and exploit them.
Not to say Rocket League has vastly changed in the last 8 years (I've played for 5 of them), but it's definitely different and a little updated.
Edit: Not to mention Rocket League rotates special game modes regularly for this purpose as well.