Because it's a vowel and always followed by a consonant, so you can always intuitively pronounce those names.

consonants vs. vowel?

I feel what your friend is saying. I'm not sure why, but the K prefix in a name always felt "unprofessional" and/or ugly.

I can't exactly put my finger on why it feels that way

I never liked them because it fragmented the space of apps available on Linux. You'd be looking for an app that replaces something on windows, and inevitably you'd find something, but it starts with a 'k' and you're on gnome. And now you're not sure whether it'll work for you, or whether you need to install a bunch of extra stuff to run one app, or whether you should keep looking for another 'g' alternative, or whether you need to just dual boot windows.