Highly contagious disease with symptoms mild enough for you for it to be safe to drive. Like COVID in early 2020.

Or, for example, if kid had accident at home that's fairly serious but not serious enough that you actually need ambulance. You want to get them to hospital quickly with minimal walking required but you also likely need parent to stay with them.

Because sometimes someone (a partner, a friend, etc.) is driving for you.

Yes, you could take a taxi, but that can easily cost more than parking, even when parking is as expensive as in London.