Well, they are, in that they're designing something to be marketed and sold, and if people see something that looks cool, they're much more likely to buy that than the one that is just boringly structurally perfect.
Fancy-looking electric guitars don't really sound better or play better based on how they look; it's much more about what they're made of and what electronics and strings they have...but the cool looking ones will sell faster to most people looking for one.
Only the ones that already know how these things work are more likely to choose one based on properties other than appearance.
(this is also true of people choosing other people, or choosing pets, etc...looks first, everything else secondary, until they learn better the hard way, if they ever do).
FWIW, if I put up two songs on the internet, one with a fancy cover art and the other with a blank one or a boring one, which one would someone listen to first (or at all)? The fancy one...I've done the experiment and seen the stats...even though the image has NOTHING to do with what you are going to hear, it is nearly EVERYTHING about what makes someone even bother to listen at all.