If I go to my local high streets I either cannot park at all (all residents only permits or disabled or taxis only or bus stops etc) or I have to pay eye watering fees - e.g. £1 or 2 per 15 minutes. Council parking wardens will be out prowling looking for infractions and giving you a £80 fine without any grace period.
...Or I just go to a shopping center like Brent Cross and park for free with zero hassle.
Yes I can walk or take the bus to the high street, but that will turn a quick 20 minute errands I to a 100-120 minute roundtrip, with the discomfort of doing it with shopping bags on the return journey (and the buss will cost you more than parking and fuel, while being slower, less convenient, and less pleasant)
For what it is worth, I don't feel like crime or drugs are a concern, at least not in my part of London.