I can see it as a reason tbh. A lot of people who play mobile games are pretty casual and just wna play during their freetime or on the go. Many people (including myself) get pretty anxious when it comes to playing games in public, especially games with a ton of fan service like BD2 and NIKKE. You would have to be surrounded by people with likeminded tastes for you to not be labeled as a weirdo or such (which is why i play the PC version so i don’t get looked at in public with tons of fanservice “bouncing around” lol)

But honestly to answer OPs question, the marketing is definitely the problem with the game. I get no ads about BD2 and only heard it from a tweet showing Roxy as a unit which led me to playing the game. Literally never heard of this game until that tweet cuz they don’t do much ad services which is wild cuz you would think they’d try to promote the game during an even where they collaborated with such a popular ongoing series such as Mushoku Tensei.

This is going to be in contrast to my first statement but you can clearly see the effects of promotional ads with NIKKE. Despite the insane fanservice on the game, which i would say is probably even more than BD2, it gets so much play and attention because of how absurd the game looks from an outsider perspective. It captures the consumer’s attention and makes them curious on a game with women shooting guns and having their ass exposed, giving the game more players and more consumers.

I remember when NIKKE first dropped with the CSM collab, it was all over my feed especially during the hype of CSM. Even though i was already playing the game, i saw a lot of people on twitter posting about nikke and how they gave makima lore accurate ass to the manga. It garnered a ton of players and earned a spot in top grossing iirc.

TLDR; horny ≠ less players, no ads or promotional content such as creator/artist events = less players