People like to hear repeating harmonies.
When you build a progression that you like and play it, you get used to it and it starts sound a little cooler each time you play it. You accept it as part of the song. After you hear the harmony enough times going into a different harmonic section isnt going to sound appropriate. It sounds alien. There are ways around this. I would search for music theory on the net man. I would tell you how I get around it but then we would both sound the same. Which wouldn't do you or me any good.
Bass guitar is the answer to everything