We tried fines a few years ago, you'd be charged a full hour if you were late, so what happened was the regular late pick ups just started picking up an hour late, figuring it was a bargain and as they were already gonna be charged for five mins they may as well take the full hour for the same price.
The staff left behind never got an extras hours wages though and faced their own problems picking their dc up from childcare themselves. Some of us knew which parents were always late and has to pay extra childcare (out of minimum wage for an hours work we won't be paid for) knowing we wouldn't be able to collect our own dc on time as it's almost certain we wouldn't be leaving on time, or arrange for someone else to collect their dc until we got home.
Staff complained and complained and the owner had to start doing some lock ups herself and soon scrapped the fines, preferring to be ten mins late home, than a full hour.
The majority of parents pick up on time, and in emergencies are very very sorry, I absolutely don't mind, sometimes it can't be helped, and it's usually a one off for most, I've never logged them for a fine.
But there are some who are regularly late, and take the piss, no apologies and often aggression, and it's easy to spot those from genuine one offs. These are the minority, but it does happen.