Expense, frame split required, larger sprocket = larger chainring and reduced ground clearance, not easy to deal with issues if they arise in the Georgian mountains (where this bike should have been in May ) Vs a chain available everywhere.
I think there's a few accounts out there of the belt being destroyed fairly quickly by mud.
Not easy to tweak wheelbase Vs a chain adding links or half links.

I had an email back from Waltly. They have one female designer and one female welder. Never said how many in total though!