There's been issues of western backlash to certain titles and censorship lately and it might be considered too risky. They wouldn't want bad PR about pai touching after all.
Pretty much this.
It maybe possible (though less likely) for English subtitles to appear in the Asian version since there are a few games like that. But, a western release is pretty much out of the question due to censorship and niche market.
Remember, the genre of the main game is an idol raising simulator. You are a producer (likely a grown man) who "raises" underage girls to become top idols. There is a lot of red flags here.
The Shiny Festa iOS was censored (ex. certain outfits like bathing suits were removed), and that was a strict rhythm game. So, you could imagine how much more censoring they will do for a main game title. For example, some things that might be censored are costumes (like bikinis/bathing suits), touch scenes (you can even touch their breasts which at few times makes a perfect communication), certain dialogue, etc.
All that stuff that could potentially be censored was there since im@s 1, so for them to take that away just for western release is totally unacceptable to me. Especially, since this is a franchise I'm passionate about. I don't want any changes due to cultural differences. I want to play the game the same way as the JP im@s fan played it.
I know, there are a few niche JP games that got release to the west. I would argue some of those are more mainstream genre like fighters or RPGs. Also, some games that get western release like PS4 Senran Kagura are rated M. So, im@s doesn't fit in those examples.
Plus, Namco is a big company. They have a reputation in the West for making mainstream games like Tekken, Soul Calibur, Tales series, etc. They likely don't want to risk negative publicity by releasing im@s in the West. Other companies don't have this problem since they're so small, and their entire business is built on localizing niche games. So, they don't give a care what anyone says to them.
Also, I think some people misunderstand the genre the main titles are categorize. This is not mainstream genre like fighting games, action, or RPGs. As I mentioned before, this is an idol raising simulator, so it's a niche market.
Yes, there's a rhythm mechanic, but that's a small part of the main game. The big part is raising idols via management and establishing relationships with them. Plus, spending hundreds of dollars of DLC to obtain costumes, accessories, songs/dances, and story. So, basically a niche market.
