If your browser ignores CSS stylesheets, it's going to have a hard time getting much traction. I suppose I could spend time crafting site-specific stylesheets

If your browser ignores CSS stylesheets, it's going to have a hard time getting much traction. I suppose I could spend time crafting site-specific stylesheets for all the sites that insist, for no good reason, on having CSS that makes them unreadable, and then tell my browser to use my custom stylesheet to override the one the site specified. But why would a site designer force me to do this? For content that shouldn't care about things like font sizes anyway?