They know who’s died in their area and likely to sell and then they cold call ... when I get a moment I’ll detail how they went about it but I suspect you know.
That’s not a rotten apple, that’s how they do business and you can come up with any amount of excuses / reasons you like, it’s filthy business ... and while they’re in the street they’ll go for a walk and have a chat to any older folk doing their gardening and mention how they were “invited” by so and do a few doors up.
Rural areas are no better, in fact worse in many cases when it comes to exploiting people ... got a beaut few stories there too. Rural people don’t bother complaining to authorities.