I hear the "X are Tools mentality a lot". It's true of guns and it's true of guitars. The only difference is you sometimes want your instrument to look professional (whether a jazz guitar or a solid black spikester for death metal), where as typically in shooting competitions/classes people don't care about a gun's look. Or, if they do, I can't figure out what's up with race guns
A tool will get the job done. A classic car which functions fine internally has no need for leather upholstering, dashboard refitting, or a new paint job. It will get you from point A to point B.
For a lot of people, dropping money on an object is a personal experience, and if it's something they hope to use a lot they want it to be something they like looking at. I like the sleek black look of my CZ 75. I appreciate the fine wood of the CZ 452. For others, they don't want to spend the extra time, money or energy.
For those who say it doesn't matter at all, would you carry a bright triple-tone 1911 or S&W Revolver colored orange, pink, and purple? If you like those colors, substitute ones that you don't like.
If the answer is that you wouldn't carry it, then you've admitted that, to some degree, appearance matters. You may disagree about how much, but it's there. If you would still carry your choice of handguns in those colors, then you can probably say that appearance doesn't matter to you.