I'm always puzzled how people get this bad. Most of them seem really old so I can only guess these are basically invalid elderly confined to a bed normally. I mean, I get blackheads in the summer and usually all it takes it fingernails and a mirror to remove them. These seem even less stubborn to remove so I'm not sure how they get so bad.
A friend of my dads has these in a similar way on his neck. They appeared to have been extracted so many times the back of his neck was perforated with holes you could easily place a BB inside . I assumed it may have had something to do with working near extreme heat from the steel plant smelter.