Cool thread. Only halfway through, but I'll chime in anyway.
Exactly. Easy answer: "Hey everyone, we acknowledge that there's some demand for wide-spaced five strings, but our current fivers are selling extremely well. No company can please everyone, and a wide 5 is something that we won't offer at this time. Thanks for your interest in EB MM".
Different strokes. I played four string for about 25 years before getting a fiver. My first fiver was a Fender Roscoe Beck with 19mm spacing -- felt great to me. I then got a Modulus Quantum fiver with 17mm -- great bass, but my right hand never felt comfortable. I wasn't even that thrilled with an 18mm Mike Lull fiver that I owned for awhile.
Could I have adjusted to those narrow basses eventually?
Possibly... but when I know that 19mm is perfect for me, then why I should I bother with anything else? Likewise, if you're comfortable on 16.5-17mm, then there's no reason for you to consider alternatives.