Well, the romance in any RP, not just 1x1, still need the agreements of both side, IMO. I mean, you can hardly have a romance if your RP partner doesn't agree to have his/her character to hook up with yours.

That said, I think people can still RP without the romance as the main focus. Sure, there might be a romance in it, but it should be as a 'sweetener' for the story. 
At the moment, I'm doing a 1x1 with Sora, and we're both playing as females. We're not planning any romance between our characters, and leave it up for our muse as we go through the story. It might happen, it might not, it might be with each other characters, and it might be with another male character that we pop in later on if it fits. 
Our main focus for the moment is character building and exploring how our chars reacted to the situation they're faced with.

So, yeah. It IS possible to do 1x1 RP without the romantic situation, it depends on the story and the agreement between you and your partner though. About the romantic related ones being more popular... *shrugs* it's not like you can help what other people like, right?

If your interest check got ignored, my suggestion would be try to bump it up to see if any would take a liking to it, or simply make a new one, maybe along with a story idea to give the reader some insight on what you're really looking for.