Why do people pick out only metallica for "selling out"?

I don't understand why ANYONE says ANY of those bands sold out. For example Metallica, OH MY GOD A COUPLE OF RICH THIRTY YEAR OLDS DECIDED TO GET A HAIRCUT!!! WHATEVER WILL WE DO!?!?!? I think it's ridiculous. Also, I am a firm believer of doing what you enjoy, many of those bands probably got bored of what they were playing and decided to change it up. How annoying would it get if people demanded of you to constantly play the same material, in and out of studio, over a period of ten years. I also believe that none of those bands would have taken time to record those albums if they didn't enjoy doing it, you have to think about them. On top of that, those bands all play their old material live, so what more do you want? If you don't like the album, don't buy the album. If you wanna hear old material, then go see them live. So, as i said, absolutely NONE of those bands sold out, maybe they were bored, maybe they wanted to experiment, we'll never know, but every true fan of those bands will respect every decision they make, no matter what it is.