You're not allowed to for example pop in and do some shopping on the way to pick-up, which I presume most people do anyway from time to time because who is going to check.

Indeed. Another perspective (not my own) is:

"I work weekends sometimes as a nurse and I get no freaking rest and recovery unless I send the kids to daycare on the one day in the middle of the week that I'm not working this week, lest I collapse from exhaustion". Not gonna lie, it's more healthy for the kids as well because it creates a better routine for them.

Or,

"If I don't pop in to buy this carton of milk for 5-10 minutes before pickup, we'll have to do it after pickup, in which case it'll take 45 minutes to an hour and the kids will be tired and irritated (and so will I) and get less sleep because of the extra time before supper and they'll be cranky tomorrow morning causing all kinds of domino effect havoc".

Both cases are worse for the kids, if you follow the rules.

🤷‍♂️ I'm definitely guilty of not following the rules 100 %. Actually somewhat proud of it, but I can't admit to it to anyone because I'll be guilty of fraud or some shit.