They don't want to touch them because its slimy and gets over everything when you take the tyre off...
Been using Ultraseal or Slime for the past 5 years with great results
If I get it changed at a dealer I warn them beforehand about it so they know to expect it.
I've started changing my own so I don't have to worry about it.
Explosions sound like an urban myth... maybe they used hydrogen in their tyres and acetelyne torch to cut them off
Anecdotal evidence of the benefits of using a tyre sealant...
Round Australia trip in 2011, up in far north-west Australia (mining country) I had to get a spare rear I was carrying fitted. Local Honda everything dealer did it at a ridiculous cost, but everything is a ridiculous cost up there.
I asked the heavily tattooed mechanic (think Harley biker type) if he'd put a half bottle of Slime in the new rear... he said " Hey I know that stuff. Used to do the postie bikes and they'd come in once a week with punctures (very rough & hot roads up there) but then they started using that and we didn't see them for months...."
So, I'll keep using it happily, each to their own.