Why not speakon?

"But I fully understand that anyone selling a product has to bow to the market, at least to some degree. "
Chayro

Nah ye gotta bow all the way to get deeper penetration :-)

Most equipment is designed for the desires of the marketplace and audiophiles want the ability to endlessly screw around with different types of connections in lieu of actually listening to music. The marketplace won't tolerate being limited to one type of connector in many cases. Even Naim, a long-time champion of the DIN connection, now offers RCAs as well. I don't know, but I believe that speaker designers would usually prefer to build speakers with dedicated amplifiers optimized for their designs, but that's another thing that fell by the wayside. But I fully understand that anyone selling a product has to bow to the market, at least to some degree.

My BMC Purevox speakers offer both connections, 5-ways and Speakon connectors.

Because they aren't made with rhodium over silver over gold over UPOCC copper? There is no real reason except audiophile expectations. They are a bit large and unsightly I guess. However, they use almost the exact same philosophy of large contact surface and minimal metal mass used by Eichmann, without the massively marked up audiophile pricing.

Spectron

Adding a versatility to the equipment, I guess should not hurt, because there are pro audio models that would offer both 5-way posts and speakon.

I only know of REL subwoofers that use this connection.Are there others?

IMO, the reason that the current 5 way binding posts are so popular in audio brands is that it gives total flexibility for the owner to use the connection they feel is best.