Maybe they are monitoring the situation with local fiat bookies and than adjusting the odds to get maximum margin while still staying highly competitive. I know for a fact that some fiat bookies employ psychologist to better squeeze the players. His main job is to hand pick those few games labeled "super bets" - highly interesting games offered with no margin or very small margin with usual rule that you have to play at least 5 games on a ticket. It is very lucrative and competitive business so it is only natural that bookies resort to all sort of clever promotions, and odds tweaks.