I have yet to find a professional level guitar player, whether pop, rock, jazz, or country, who does not have an intimate knowledge of theory and scales. Yes, I'll admit, the Guitar Centers (Banjo Centers I like to call them) of the world are filled with guitar-wanking-Petrucci-wannabees. However, I think if you're going to rise to the top in any guitar genre the requirements will ultimately be the same.
I think the biggest difference here, as Derek pointed out, is the attitude of the teachers. Most guitar teachers of beginner students of pop and rock are not going to get too excited about whether you know what you're playing, they're more interested in whether you FEEL what you're playing. Personal expression is a key driver in improvisation. The ability to emote through a musical instrument is a critical factor in the early stages of guitar instruction. It's all about catching the feel. In other words, who cares what it's called, let's make music.
I think the piano teachers who use the an approach to develop first the love of the music are the teachers who ultimately end up with students who are depressed when they can't have a lesson.
Let's face it, theory is something you use to analyze music once it is composed, not while it's being composed. If we develop curious, music-loving students, the desire to understand how music fits together will develop naturally.
Jef