I can former.
Parent on zero hours who will lose their job and nobody eats if they are late, babysitter 5 minutes away.
Isolated lone parent, dc with chickenpox or similar.
Someone in food poverty who can't buy dc's breakfast, or top up the electric until their wage goes in, not wanting to drag their cold, hungry dc to the shop opposite in the pouring rain.
I was once someone's last try for childcare before they left their dc, aged between about 6 & 10 home alone all evening. It was that or lose their job, not get paid end of the week as needed for essentials, and back on benefits & dire poverty. And benefits or getting the wages owed wouldn't have been paid on time to buy essentials. Luckily she chanced asking a parent she didn't know well, and I was able to help. If she hadn't, then she'd have been desperate enough to be forced into the decision, not neglectful.
I've also had a neighbours toddler shoved at me during an unpredicted and unavoidable crisis with another family member, which thinking about it now at barely 3 they must have been unattended in the house for at least 5 minutes. The parent was in easy hearing distance but in the circumstances wouldn't have made the usual safety precautions like closing safety gates as you would when popping into another nearby room.
I'm not saying that any are common scenarios, but it's very sheltered to think they don't happen.
Funnily enough I thought about this earlier at the corner shop when I saw someone run from a house opposite. It struck me that they were closer to any potential dc in their home and back quicker than someone in a larger property putting the bins out or unloading shopping.