Timothy
If you do not like people doing the CD reset, as it is also known, then, ban it, if you are a league host. You could also ask your host to do this, but they may not say yes to the idea
I run a league where the CD reset is fully banned, with repurcussions if it is done. I also run in leagues where it is not. That is up to the host or league management team that runs the league.
In the end, this is just a game and you should be able to enjoy it as you wish.
I don’t believe the OP is talking about car resetting. I think he is referring to people moving around leagues which still ends up as the same answer you provided. It’s a game for enjoyment and you are free to play as you wish (within the rules).
In addition some will find a league too strong for them and will move to an alternative more appropriate or maybe they can longer play at the time the league runs or might need to take a break for rl reasons. I also believe you can outgrow a league and if you are wanting to progress and challenge yourself you often need to move. The difference in standard between the average Elite tier and the top leagues is huge.