I think I know why. Note that this is only my opinion. In the game, you are the main character. You are important. There are all these amazing people that you grow close too, and you matter to them. They love you, they care about you. You are important to them.
In most dating sims, even if you don’t do their route, most characters still like you. They’re still your friend, you still mean a lot to them. In dating sims, all these amazing (and attractive) people care about you. They love you, and they care about you. And when the heroine is relatable, it feels like it really is directed towards you. When you play dating sims, you feel important. You feel cared for. You feel loved.
having been with bitty for a few months now already and been friends with him for even longer, he knows that bitty can get a little uncomfortable when jack starts spending too much on him.
so he takes every opportunity he gets to put them in situations where they’ll get fined.
he wants bitty to be happy. and he knows that bitty is the happiest when he’s baking and taking care of the people he loves. so why not kiss and cuddle with bitty in front of their friends? they know and are happy for them. and he gets to indirectly fund bitty’s trips to the grocery stores.
as far as jack’s concerned, what matters most to him is his boyfriend’s happiness and wellbeing. and through the sin bin he can still be part of the haus. he could still be part of his friends’ lives, even when he’s an hour away in providence.
so jack visits the haus as often as possible, and he kisses and kisses bitty, and encourages the pet names in front of his friends. it makes him happy. it makes bitty happy.
and, as an added bonus, it keeps his boys well-fed.
(and clean. wait a few more kisses for that dryer, dex.)
• you’d probably go over to his house and all. Like his mansion because he’s just that extra.
• and he leads you to a room and you look around to see nothing in it except this huge, four poster bed with silk sheets that were imported from France and mahogany from the forests of Bulgaria or something.
• he busts out the fancy alcohol. he is 94% likely to also bring out some shiny crystal glasses that cost more than your entire job’s life salary at MACUSA and he sits there, casually sipping wine or champagne or something that he says was one of Merlin’s own personal collection.
• probably lots of excessive eyebrow raising and sexual side glances and all. yeah. whatever it is that people do in fanfic.
• you giggle or something and flirt very unsubtly and keep offering him glasses of his own alcohol.
• percival is a very heavyweight but darn if you won’t get him drunk. three bottles and four hours in, he conks out in the middle of his very fancy and expensive embroidered sheets.
• you slip out of his house. underneath your coat, a glimmer can be seen.
• your goal this entire time was to steal those crystal wineglasses. you live out the rest of your life on the beaches of the Caribbean or something, after having successfully pawned off the glasses.