I'll start with myself. I entered into web development without learning HTTP (and I'm sure most people do that even today). I began with HTML, then CSS, then JavaScript, then PHP. The moment I got to PHP and worked with such things as cookies, sessions, redirects, I was super super confused.
Had no idea what I was doing and why I was doing it the way I was. For example, back then in order to instruct the browser to redirect to a different location, I used the following code
header('Location: https://www.example.com')
I always wondered "What the hell is this weird looking statement." But then once I learned HTTP and its technical details, it all made sense. In essence it made me a much more confident web developer.