Thanks for your reply. You mostly got where I was coming from. However I'll explain some more.
The XP in PM64 and TTYD was on a sliding scale. For example a Gooma gives you 10XP at level 1, 5 XP at level 2 and 0 XP at level 3. So you can't infinitely farm XP to max level early on. Sure...
lol gameXplain.
Moving on from that.
The treehouse had a limited time to show us a specific amount of content. So they could not waste the time away in battle after battle. That's no indication that battling is pointless. However others have noticed that there is no unique reward gained only...