It's a personal headcanon based on aspects of life on the lion turtle that are not directly addressed and how Wan (and others who are poor) are shown to be treated. I don't mind explaining at all! I'll start with stated and implied canon and then where my extrapolation goes from there!
Stated canon: -The people of his city think they are the only human settlement in existence. (From his conversation with Aye-Aye about other lion turtle cities) -There is limited space for living on the Lion Turtle (everyone either lives inside the walls, or just outside the walls but still on the turtle's back) -Being banished is considered a fate worse than death until Wan proves otherwise (Yao's mental truama from being possessed, the awe in the lead hunter's voice when he talks about Wan, Jaya's declaration that "wan has proven" that humans can survive in the wilds) -Wan was not happy with his place in life and was willing to do things to try and actively change it. -Wan is sensitive about people implying he isn't worth as much as others (until after he spends time with the spirits and mellows out)
Implied Canon: -Most homeless people are male (none of the people shown in the fight against the chous or among Jaya's refugees are noticeably female). -Most homeless people aren't trusted with jobs which reduces their prospects for prospering within the city (the lead hunter having to be convinced to let Wan join the hunt despite there being no other volunteers) -Homeless thieves are looked down on, but not to the point of actively punishing for their actions (the chous knowing Wan by name and tolerating his existance despite the theivery which is implied to be a regular thing - wan only getting arrested/banished because he stole the power of fire) -Much of the 'background' culture is based on the Zhou Dynasty of China (fashion and home styles incorporated, also a pre-Qin (chin) dynasty; matchmaking for marriage and marriages in general became an established custom during this same time period)
Headcanons that formed from thinking about all this and trying to figure out what Wan's life was like before we meet up with him: Due to the limited space for humans to grow and have families, marriages were likely highly regulated so they benefited the community at large. Determining if a match was good for everyone would involve a lot of fortune-telling superstition based on birthdays and other omens. Most marriages would not be love matches - though love-matches were, of course, considered a good thing when they happened due to the harmony of the match.
One major thing that factored into this was likely the value of female children over male (leading to male children given up more often than female, hense more male humans being homeless).
Wan, not being content with his lot in life, would see marrying into a family - any family - being an easy way off the streets and to a regular 3 squares a day for him (and likely Jaya and Yao, who he had taken responsibility for). However, as a homeless man who most people wouldn't even trust with a basic job, he has pretty much nothing of value to offer another family except that 'he was born on a lucky day'. So of course he would be rejected by any matchmaker he went to for that because he was never 'good enough' for anyone when there were a plethora of better men out there, both homeless and otherwise.
Wan thinks it's a fast track to a better life, so he's focused on it in a new place with other humans out of a fear that the good stuff he's gotten so far will disappear. He just wants to feel valued for who he is and this is a way he's familiar with. He's also gotten what he perceives as romantic attention which he's not used to and well, he's 18. He's going to blush a lot and pursue what he can. In canon, there were spirits around, he realized after fighting to protect Mula he was 'tired' of other humans, and didn't need to worry about what other humans found important anymore.
He's actually going to mellow out after his first month there and he realizes he doesn't have to prove himself in any way. I play him as grey-ace (though very romantic), so anything that does happen wouldn't go very far anyway as he'd have no interest in it beyond feeling valued by others.