Technically, BL is a subgenre of romance, but I wasn't referring to BL when I said "romance."
If I'm understanding what you and @UbePie mean correctly, is that "narrowing down audiences" easier because of the niche market for BL comics? As an example, Fantasy is a broad genre, with many subcategories, whereas, BL is already a subcategory of Romance, regardless of what other genres are attached (such as murder-mystery).
And of COURSE cis-straight romance is everywhere in physical stores, haha! The traditional publishing industry does not evolve as quickly as the web. For hundreds, hell, thousands of years, people have been writing stories about straight couples, because of societal stigmas, so it makes sense that bookstores would be littered with them.
Look, I'm not trying to attack BL books/comics. I think they have a great deal to contribute to the storytelling industry, and I personally read a few myself. This whole thread was about ways to be noticed on the platform if you are not writing a popular genre. Popular on this site specifically. You shouldn't feel like you need to defend BL comics as a BL creator. No one, or at least the majority of us, were not trying to belittle the mentioned genres.