Great question and made me think. I think the difference may be that people that need to stretch payments for smaller purchases tend to build up credit card debt and fall into 18% APR for years and never get out of it.
Car loans and Houses have a very controlled lending market. Even more so with business loans.
I think there is big difference between monthly payments for a Go Pro camera and debt financing your new restaurant.
You might say that buying a house on credit isn't frivolous but a pair of shoes on credit is, but where do you draw the line in the middle?
(Disclaimer: I work at Square, but I am otherwise completely uninvolved with this acquisition or product area.)