My sister watched me frost a cake and asked why I was doing it wrong, she was right
I've been frosting cakes the same way for years, just plopping it on top and spreading it around. My sister came over on Sunday while I was making a birthday cake for my kid and asked why I wasn't doing a crumb coat first. I told her that was just extra work, but she pushed me to try it, so I did a thin layer, stuck it in the fridge for 20 minutes, and then did the real coat. The difference was crazy, no brown crumbs in the white frosting at all. Has anyone else skipped the crumb coat for years and felt dumb about it after?
The part about "no brown crumbs in the white frosting" is what gets me, because that is really a texture problem more than a looks problem. When you skip the crumb coat, those loose crumbs get pushed around and end up sitting right at the surface, and then when you drag your spatula over the top coat they tear little ridges into it. So you are not just hiding crumbs, you are giving yourself a smooth base to glide over. I learned this the hard way doing a red velvet cake once, and the frosting looked like it had dirt in it. The other thing nobody mentions is that the crumb coat firms up the whole cake, so the top layer does not slide around while you work. It takes 20 minutes of waiting but saves you 20 minutes of cursing.