I had hundreds of coins sitting well before I defeated the first boss. Even with a mouse that has a spam left click function collecting them was still tedious. It's simply poor design.
That's because you haven't been active in the game, otherwise you wouldn't have a piece on the ground!
Just kidding, that's the intended effect, you're frustrated because it's painful. Then you get a reward that automates something painful.
I think it's pretty well done but it can't please everyone and there's no problem!