You aren't wrong, but the _overwhelming_ majority of "full stack" devs I've worked with only know CSS at the most basic level and have little interest in learning it in depth. I myself have been programming for more than 20 years, doing web dev for almost 15, and I can't find the motivation to learn it well. There are too many technical skills to keep up with and CSS is pretty low down on my priority list. I would prefer to rely on specialists who are experts but companies aren't willing to hire dedicated front end devs.