Well, of course. Let's keep the minimum tank size and the maximum bio-load and the compatibility questions separate - they are all different questions. I'd never have such a scarcely populated tank either, unless it is for a fish that must be kept solo. Obviously, it is almost never that a hobbyist keeps one 1" guppy in a 5 gal either.
That is a philosophical question rather and we (perhaps?) better stay out of it: what is better for us as a humankind - to never subject a fish to a captive condition and end up knowing little-to-nothing about them or to capture them and study, interact, enjoy, and learn about them?
