Anything that is more convenient than things were previously can be seen as decadent. I suspect so much that everyone takes for granted today would have seemed decadent to people 50 or 100 years ago.

Maybe there's a number of people that such a service would really help out? I don't know, but single parents are one group that comes to mind. For helping them get items that they can't easily go out and get themselves because of having to stay at home with the kids. It's hard to predict how new services may end up being used and being useful.

Maybe the current cost is too prohibitive for many people at the moment (i don't know what they charge and don't live in the US so wouldn't know how to judge the figures anyway), but if such a service proves useful and popular maybe the prices will come down. Anyway, I don't see anything inherently wrong with a service that not everyone can afford.