Of course people are accidental landlords, don't be so silly. Examples:
-2 people move in together, but both have a flat so they move into one of the flats and rent the other out. Because perhaps it's a trial, they don't know how it's going to go and the person leaving their flat wants some financial security
-you buy a house and your job gets moved and they give you accommodation. You don't know how long it's going to be, so you rent your house out whilst living in the other accommodation
-you decide to work abroad for 18 months so you rent your house out.
-you rent out a house you are struggling to sell as part of someone dead's estate
These are all accidental landlord scenarios. It means it wasn't what someone set out to do. It doesn't mean they tripped over and their dick squiggled a signature on a rental contract that happened to be laying on the street.
And no I've never been a landlord. But you are being silly.
But what now happens - I've read exactly this on MN - someone's adult child had a flat in London but decided to go digital nomadding for a year. He decided against renting the flat out for a year because of the potential downsides. So housing stock is depleted because people are too scared to be landlords. This person literally would prefer to forego thousands and thousands in income because the potential downsides of being an accidental or little landlord are far too large.
So there's fuck all to rent and renters lose.