There was plenty of room for those songs, but I'm guessing that Allen Klein didn't want to give us too much bang for our buck. Most US albums (pre-Pepper) had 11 songs and sometimes 12. Hey Jude is the only one that has only 10. I guess he thought "Hey Jude" running over 7 minutes justified only putting 4 songs on Side 2. Just record executive greed, so they wouldn't have to pay as many royalties.