My understanding is that it's one of a few companies that'll come along and take away your deceased relative and have him/her cremated then bring back to you the ashes.
The advantages are that it's simple and cost effective, so there's no service to pay for, no funeral cars, no flowers, no coffin, etc etc.
I know of one person that did things that way. The advantages are clear. Less financial stress and less organising and the stress that can bring. Of course it takes away the chance for the wider family, friends, workmates and so on to mark the passing and pay respects. Although you could always have some sort of a wake or whatever gathering afterwards to celebrate their life I guess.
I think it's certainly an option for people that aren't religious and perhaps for those who are so old that their peers have already gone on before. Although I do wonder if those left behind might feel a bit left out.