Music is a question of tastes and sensations and like other forms and expressions of art not all of us feel the same way about it. I personally do not feel a lot of appreciation for hard rock but I respect those who think it's the greatest thing in the world attributing to be the best and most complete style of music.
Not all music is suitable for all ears, that's why some are able to appreciate some musical styles more than others.
Another factor determining that certain people do not like hard rock is that they attribute or highlight violent messages, sexual and in some cases satanic, hence many consider it "the devil's music".
Because it sounds terrible to them. The electric guitar is a mainstay of rock music of all genres. The quintessential distorted sound of an electric guitar is a happy(?) byproduct of low-fidelity amplifiers that existed in the 1950's and the 1960's. Many musicians found the distorted sound appealing.
You really got me by Kinks (1964) was one of the most influential examples of the use of the distortion effect. In this case, it was purposefully created by piercing a speaker cones with a razor blade.
Not everybody is a big fan of the distortion. Some people find it irritating. Such irritating elements overblown are the point of heavy metal. Very distorted guitar sounds, screaming and lyrics about themes like violence and obscenity are the what heavy rock, or heavy metal in particular are made of. Interestingly, heavy metal is particularly popular in the peaceful and prosperous north of Europe. Those corners of the world where conflicts are commonplace heavy metal has little popularity. Perhaps heavy rock and heavy metal in particular are ways to artistically express the uglier side of the human condition. Where and when the horrors that heavy metal or particularly death metal bands sing about are acutely present, people tend to prefer their entertainment to be on the lighter side.
Cuz they uptight bitchez. 🤣