When I said that it was a necessary part of the infrastructure, I meant that it was so according to the halacha in RaMBaM under discussion (end of Sanhedrin ch. 5). I guess since our communities are structured differently than they were back then, they have different needs. After all, the RaMBaM’s calculation was based on having a bes din of 23, a single melamed for the entire community, and other things that aren’t part of our system today. Does riverdale have a tanner? Flatbush doesn’t.
off-topic: You teach at Einstein? Do you know… (modern orthodox equivalent of mikvah gossip ensues)