I think part of this is down to how most people now do it themselves online.
When you used to use a broker (for us old farts) one of the questions they asked was about work, "do you use it for travelling to work?" "yes", add commuting
"is that a permanent place of work or do you travel to other locations as well" "Only one" : Non business "more than one" : add business. "Then how many miles etc"
Because online they are trying to make it as quick as possible they seem to actually make it harder to do quickly because in my experience when you go to the insurers site from the quote site its almost always wrong, so you do it again just to get it right then get a diff premium etc.
The reason you now get asked more questions is that the insurers quote engines and stats are now better. They know more of the risks and they can easily include more factors.
I dont believe SDP should automatically include commuting. Plenty of people don't work. Second cars, stay at home parents, the retired etc.
The more worrying one for me is that a lot of people should have some ;limited business mileage, and it costs naff all, yet most do not.
If you do anything like taking stuff to the bank, post office, nip round the shops due to running out of coffee, giving people a lift for a works event, even attending a works event in your car your doing business miles.