I have different POV, I believe they are playing for the competition since I have seen those who are on the leaderboard are mostly betting with the minimum bet for the competition.
Betting $1 per spin can lead them into 2 different competitions (multiplier and races), if they play for rakeback mainly for rakeback, I dont think they will bet $1 per spin because they can do something like 0.2 per spin 5x which will give the same rakeback as betting $1.
The winners of the multiplier contest are mostly the same names every day (including you LOL) as you are always on the leaderboard.
However, my point of previous post is just a suggestion to make the competition become more interesting and I'm sure you agree with it.