I like advancing in levels because it feels like I accomplished something. I don't get that nearly as much for Levels 3-8 because I can do that in two three days. A level that I worked for, that I did things more than just kill endless goblins - that meant a lot more to me.
Alternatively, given you can do nothing but stand around and talk about your day in the square and earn XP at the same rate, why does that level mean something to you?
I agree with your general principle -- going on a quest to discover artifacts before a lich finds them and then confronting him in his lair and gaining a level as a result is far more epic than "killed goblins for 10 hours" but how is that actually realized in-game? Trying to understand your perspective here.
But if you are around lvl 10 you can already make meaningful contributions to a lvl 16 group, you just have to find out the way. For example you can cast buffs and heals instead of others, making it possible for the higher lvl characters to save their spell potential for offensive spells. On lvl 10 a Bull's strenght and others hold long enough to finish a dungeon. You might summon creatures just to provide one more target for the enemies, and reduce potential flanking situations against the frontliners. And so on, and so on.
- Cannot cast buffs.
- Have no healing abilities besides Healing Kits but those are pretty awful with zero Heal skill.
- Cannot summon creatures
- Cannot contribute effectively with a ranged weapon
- Cannot disarm traps/open locks/find secrets
Sure, a level 10 mage has some things they can contribute to a group despite being lower level. But how about a traditional fighter?