First of all, am not a big fan of trading contest because you will act and be taking trades you shouldn't have because you are desperate, ...
Contest only leads to rash decisions and poorly entered positions. You can make good money from long term trading but if you are going for these contests, they lead to the complete reversal of the buy-low-sell-high system.
It is because exchanges love people who make rash decisions and lose money. Trading fee is also another factor that brings them money.
It is best to avoid them as much as possible rather never participate in them. Be the long term trader with goals for stable profits.
Usually these trading contests are part of their marketing tactics which attract peoples and also increase their transactions if someone wants to avoid them it's never been problem because no exchange or site can force anyone to join this without his wish.
Here I completely agree about this mostly exchanges wants peoples to join and then lose their funds in these because this will increase their profit which is always important for them and they always organize these competitions just because of this. Peoples love to have their own way of trading because mostly this give them good profit but due to these competitions they lost their momentum and things gone on wrong side for them for me having these competitions never been favourable.