Pure Lego only builds are one of the several battle lines in the greater Lego community. Lego purists make all sorts of great points as their reasons for their purity, and I, in fact, agree with most of them.
Nevertheless, I am not a Lego purist for one simple reason: I am not infinitely wealth, and I like to build big.
The fact is that, in order to get the volume of especially basic bricks I need for some of my builds, I simply can’t afford to build with pure Lego. Maybe, someday, I will be able to, but until then, I include non-Lego bricks in my builds so that I can build at all.