For a 3-D printer to be useful to a home consumer a bunch of non-obvious conditions have to be met-

1- You have a need for an object you can't pick up at Home Depot, dollar store, etc.

2- You need the skills to model it in a 3-D program and make it suitable for printing.

3- You need to not have the skills to make it some other way- whether in wood, metal, or clay.

I think the combination of 1 and 3 is probably the real killer- all the hobbyist model makers, cosplayers, etc who would have the most use for one already have the skills and tools to make stuff in other ways.