Sometimes you get legendary creatures that just don't have any support in their native colors, though, perhaps because they were designed for the set rather than as a standalone creature, and as a result, they simply become bad for the role of a commander despite having a ton of untapped power behind them.

Look at Noyan Dar for example:

Comes from a set with a multi-color matters theme with a heavy focus on lands. Sadly Noyan Dar is White and Blue. He cant play with any Green cards at all, despite the fact that in the set he was printed in was all about experimenting with color variations. In order to get him into a deck with green cards you have to pick an entirely different commander, and when it comes to other Bant commanders who interact with lands... well... There just aren't any, you have to go all the way to Four colors with Kynaios and Tiro of Meletis just to get a commander with those colors who so much as mentions the word 'land' somewhere in the textbox. And that's sort of a sour point of contention when your card becomes far less useful within the 99 because you're losing an entire slot so you can run a different legendary creature you don't even want as your commander instead.