I think some professional bands still subscribe to that belief system (play fast as you can withhout regard for melody/phrasing.) I used to think that progress on the guitar was being able to play scales to a metronome faster than last month. It's really not. Ever since I got into jazz, I realized that playing single notes fast is a very, very small part of what you can do on the guitar. I still practice scales, but I also practice chord voicings (even if you're lead, being able to throw chordal stuff in is always good) arpeggios, sight reading (if you ever want to play in college/high school with a school band, you'll have to) having good timing, all these thigns are just as improtant.