It was mentioned that black and white comics have been promo'd in the past and i imagine it can happen again though i wonder if it's not so much content or style but rather readability. Tapas is a part of the mobile market so a comics got to translate both on desktop and on phones.
One thing that stands out on names mentioned like flower eater and long exposure was their readability. They had details but also clarity. Fonts play into this too I'm sure. Too tiny and people can't read or enjoy it. Too big and you can't see the art. and with regards to the art can you distinguish everything from characters to backgrounds and so on.
I personally make colored comics but I like the black and white stuff too but I've got to be able to read it if i wanna enjoy it.
Personal preferences of an audience can't be controlled though so if it's something you want more of raising your voice about it and showing off good black and white comics is a good start. Finding like minded folks also helps and as some of the replies show there are people interested in the type of content you're concerned about.
But hey maybe someone could start a thread for black and white comics just to kinda show how many of em are out there. What with so many series on tapas something like that could help reveal some hidden hems and give em a boost