I think people mine eth because its well known and its the only gpu minable altcoin over $1000 on a regular basis so the uninformed think it will be more profitable
depends on the hardware you have, amd rx cards are so so on every algo but crytonight and ethhash
so if you have those u should be mining eth or orher cryptonight clones.
Nivida 10x cards have way more options, probably best on nicehash