No Pagination for some Search Results?

I thought I was taking crazy pills, but for a lot of forum searches I often see “Showing results 1 to 6 of 23” (or something along those lines), with no pagination links for the rest of the results.

In this case, I searched for “substance” and got this:

Whereas, when I searched for “search” (to see if anyone else has this issue), I got: