Eh, Yun is overly obliging but he does also tend to get favors back pretty often. His relationships involve a lot of back and forth, even if he occasionally gets dragged into stuff - Myu's and Taku's groups are always willing to help him even before he offers rewards, the crafting guild gives him a lot of preferential treatment (yes, he helped a lot with the founding, but they've always been generous to him), Sei wants to spoil him as his older sister, stuff like that. It's not like he gets nothing for his troubles, and mostly gets completely overrun by people who tend to overrun everyone, like Mikazuchi.
Also, it's a comedy. "Here we go again *laugh track*" is a tried and true setup for getting events going with the straight-man.