Resets achieve two goals one is the keep the top of the ladder from getting stagnant and honestly that’s debatable in this game.
But the other factor is Seasonal rewards… there is a significant bump in rewards for those that surpass the reset line. 5200 is 2600 dna 5800 is 4200. That 1800 dna is significant considering you only get 2600 for your first 5200 trophies.
Is it a slog and a grind to get back up? Yes and That’s why the rewards are higher.
The reward might not always be worth it and that’s when you decide to take it easy during a season and not really push for trophies.
If you don’t care for the rewards there is literally no in game reason to push back up.