As in, your score for the season is the peak amount that you had achieved. Got up to 1k+? Great! Want to keep playing and get a bad group of randoms? No worries, your highest rating number is kept to determine your ranking.

As of right now, a lot of people are getting high rankings and then just... stopping. There is no reason to keep playing. In fact, continuing to play can be more damaging than good. This is not really good for the longevity of the game.

If your max rating attained was kept as your 'permanent' ranking, one could continue playing without worrying about losing it. If you go below it, it stays at your max, and if you go above it, your max adjusts.