...that's because I to IV is the same relationship as V-I.Hence I (in C is CEG) + 7 =CEGBb, the Bb wants to resolve to the 3 (A) in IV (FAC)
Or:
I (in G is GBD) + 7 =GBDF, the F wants to resolve to the 3 (E) in IV (CEG)
Cycle of fifths again.
It still sounds crap
EJ