I'm pretty sure they actually use their data-mining advantage to make their betting offers as attractive to regular users as possible, and therefore maximise profit.

It's so easy to just ban any user who gets "too lucky" (simply ban the top ~0.1% of your userbase every week) why waste resources on offering actually fair bets? And the requirement for "fair bets" probably interferes with the requirement for bets to be as attractive to "regular users" as possible.