People are just as guilty of this in the Ham world as much as the CB. Trying to sound like FM on the AM or SSB modes is like trying to squeeze blood from a turnip, they are different modes and operate with their individual characteristics so their sound is naturally different. FM's quality sound is derived from frequency deviation so as the modulation increases, so does the bandwidth at the frequency of the carrier wave form. This is what gives FM the superior sound and why it's the mode of choice for commercial broadcast music and broadcast TV before they went digital. Unless people have an old car with an old radio that is AM only, FM is what most people listen to for rich sounding audio for music. The only time I listen to AM is for news radio or to catch a ball game when I'm on the road.
Car stereo receivers don't do AM radio justice. It will never sound as good as FM mainly because they can't use that kind of bandwidth, there's just not enough room in the am broadcast band. I have noticed some AM stations are wider than others in my area. When I first heard some local AM stations on an sdr 20k wide with decent speakers I was impressed. Some are filling every bit of 20k some much less.