having been learning piano for about 6 years now. i never learnt any theory.just got on with learning tunes i like to play.i am now studying music theory and how to read music properly.i am ok at deciphering music from sheet music.so how important is it to practice scales ?is it worth knowing all major scales in every key ?i am really enjoying learning the theory.and i feel my playing will drastically improve now.thanks in advance.