I think this is just sort of inherent to how the indie AVN scene works- people come for the smut but they're also long-form games that may take years to complete, updating one month at a time (and that's a fast pace!). So for a lot of games there isn't necessarily an easy answer to "the MC just met these characters, each update covers one day of in-game time, on the one hand my players won't wait a year to see a sex scene, on the other hand how do I make a sex scene happen Day 2 without it seeming really rushed and unnatural".
I think some games get around it by a variety of girls- e.g. some college games will send the MC to a party where random sorority girls are happy to get laid without knowing their partner's name, while developing the main love interests at a slower pace.
Other games may start the MC off in a relationship of some kind, so e.g. he starts the game off having sex with his wife before spending a few updates building up to sex with other girls. But then some players are passionately opposed to games where the protagonist starts in a relationship.
Personally I think more games should drop the "one day at a time" pacing. It's a little unusual if a girl falls in bed and passionate love with a guy after a single day of knowing him; it would make more sense if it were clear that a couple weeks had passed, they'd been talking/texting/hanging out throughout that time, and only a couple noteworthy interactions between them had been shown onscreen. (As a side note this would also make it much more feasible to include pregnancies that actually progressed to birth without magical "gestation is 9 days" handwaves... which is something I and I think a lot of other people would really like)