Marriage as an institution is something that historically was not romantic. It instead existed to bring families together, create community bonds and provide stability in times of trouble.
Sadly, it was co-opted by romantic propagandists, and now most people associate marriage with romance. Marriage, in its altered form, is used as a tool to create "haves" and "have-nots". Gone are the days it brought people together and fostered community. We all know that nowadays, most marriages snuff out platonic friendships, and isolate us aros from our friends and families. That is why I can see why many aros would be turned away from what marriage has become, but on the flip side, I can also see why many aros would want to take back marriage and bring it back into a platonic realm.