If your account is abandoned completely without wagering single cent, it is reasonable if you get so low amount for the bonuses. Although there is something called by based amount but it wont make senses if a casino give you the same amount all the time while you are not playing. However you should be happy enough that you still get something even though you have abandoned your account. I think there is no other sites give you bonuses while you are not playing anymore.
That is something unique up until now I think from Stake,if they give you whatever amount for bonus even if you have not wagered a single cent.Most other casinos which offer these kind of tiers they reset them every month by keeping the players to wager if they want to get these bonuses.I personally like the Stake way of rewarding every bet,my percentage is still the same until I reach the next tier no matter that a couple of months have passed and not reset every month,I only gamble like 50-100 USD weekly or sometime even lower.