Just to be clear, I meant this in the sense of those potential converts to the Baptist faith. I didn't mean that other Reformers do not think their infant baptisms matter. :) I'm just not aware that many "other" Reformers wind up transferring to Reformed Baptist. (I don't know.)
I'm speculating of course, but I think because there is so little difference among us in doctrine that it would be more a result of geography. IOW, a job transfer and the closest Reformed Church is Baptist.