Oh hey, I pop back on and
this is still going on, okay .. *rolls up sleeves*
It's not a question about personal life/boyfriend and societal issues specific to this case. There have been
cases in the past where AKB48 or other girl group members have resigned due to information leaking out that they have boyfriends. These groups typically have explicit rules on "No boyfriends!" -- so it's a professional contract issue.
The bigger issue really is about the fanbase that demands this. (As said previously, I personally think that all these obsessive fans are all useless wastes of space) It's a big enough deal and apparently commonly accepted enough as normal/expected that even the Bakuman manga did an arc on it! If I were to ask and say: "Do other female entertainers in the anime/idol/etc space that do not sign these "no boyfriend" contracts still face the same flack?" -- answer is likely yes? Is that a problem?