Getting an interest from bitcoin is lucrative in any case. Normally you get zero interest at all, you just keep it on your account and it makes no profits for you and that is not taxed of course because there is no profit.
However, when you get 4% a year that is still a profit, maybe some people find it harder to like something that looks so small in a market that is as volatile as bitcoin but everyone forgets you do not get 4% in fiat, you get it in bitcoin so even if bitcoin becomes $50k tomorrow you are still getting that 4% anyway. If you have 100 bitcoins and get 4 bitcoins per year, paying 2 bitcoins as tax still means you made 2 bitcoins profit, it is still a profit no matter how much because you can't get anything like this anywhere else in the whole world.
However, when you get 4% a year that is still a profit, maybe some people find it harder to like something that looks so small in a market that is as volatile as bitcoin but everyone forgets you do not get 4% in fiat, you get it in bitcoin so even if bitcoin becomes $50k tomorrow you are still getting that 4% anyway. If you have 100 bitcoins and get 4 bitcoins per year, paying 2 bitcoins as tax still means you made 2 bitcoins profit, it is still a profit no matter how much because you can't get anything like this anywhere else in the whole world.
4% of 0.001% is always a profit no matter how you look at it, but as I recently found out, there's every risk to leaving money lying around for you to look at every day. The temptation to simply use it to gamble (not just the profit but the actual balance) is there and it's a huge risk if you're not disciplined.
But in any case, no different from any gambling site, so the fact it gives free money just for having a balance is huge.
