My father died alone and his body wasn't found for a couple of weeks. It was only via a series of coincidences that my siblings and I were traced as his only relatives and informed of his death. He wasn't a nice man. Far far from it.
If he'd ended up in a ditch or somewhere, no-one would have known who he was. He hadn't bothered to contact me or my siblings in over 30 years when he died, so we would never have reported him missing, we didn't even know where he lived. He wasn't particularly liked so I don't think anyone he knew would have bothered to report that they'd not seen him in a while.
Of course - objectively I feel sorry for this man, his life a waste. A sad, lonely, bitter, man with a horrible history. I'm sure he was an innocent baby once so life must have destroyed him. It's not his fault I guess.
However, I'm sure there are many people who are cut off from family or friends, perhaps are not that nice, have dark histories. Noone would know or care if they were missing.
Sometimes very sadly, drugs and prostitiution are involved in Jane/John doe cases and that upsets me a lot. That people got to that place.
Sadly, there may be some lovely people, young and old who've got themselves into tricky situations that mean there is noone to report them missing or join the dots.