When you use inline styles for everything, you're making the initial development a little faster by making future maintenance and changes a lot harder. (Like, if you decide headings should be italic instead of bold, that's a one-liner fix if you're using CSS properly, but if you're using inline styles you have to individually fix every heading on every page.) So most people have internalized "don't use inline styles for everything" as a general rule.

But if you don't actually care about that sort of future maintenance (or you're charging hourly for it), then using inline styles for everything looks really attractive to you! But you can't literally use inline styles for everything because even non-experts know that using inline styles for everything is bad for future maintenance. So instead you pull in Tailwind so you can say you're using a CSS framework.