I solve for this by stockpiling small bills in a drawer from which to replenish my wallet. I add to the pile by specifically paying with a large bill whenever the pile starts to dwindle, and I use a card whenever possible otherwise. The trick is to not habitually spend them except in situations (like tipping) where there's no reasonable alternative.
That makes sense. I think part of the problem is I'm trying to play both sides and mostly use a card for normal purchases, and mostly use cash for smaller purchases/tips. So you're right, I'm almost never using cash in situations that net me more small bills than I started with.
If I was a bit more consistent about occasionally just paying for something normal with cash it would possibly be more sustainable, right now I usually try to break apart small bills specifically when I'm completely out of them or when I know I'm going to need to tip someone in like an hour.
Also yeah, having a stockpile would probably be a good idea, since right now I typically only keep enough small bills to get me though my immediate tipping needs and no further, so any surprise situations mean I'm immediately out of small bills and can only pay for things by card.
Regardless, definitely more management than I would like to do, so I get why people might want a system that doesn't force them to think about that stuff at all. It's just that the alternative digital systems come with other downsides.