There are some sites and implementations where infinite scroll makes sense. Pintrest. Twitter. Facebook. Forward-reading story sites (start at page 1 and read to page 200).

There are also implementations where it makes no sense ... like the traditional reverse-chronological feed of a blog/news site home page. Or a resume. Or anything really that silos content by page.

Does it make sense to enable infinite scroll by default in a WordPress theme? No. It all depends (as always) on what you're using the theme to power.