i am simply dumbfounded why such product is so hard to come by
It's not hard to explain - there is no good practical reason to have such a product. Mainstream race wheels are all factory built with much lower spoke counts, and general training wheels have to go on hubs which are almost exclusively made in 32h these days. The few boutique hubs made in other spoke counts are aimed at weight weenies who are likely to think any more than 24 spokes is a pointlessly large amount of steel to be dragging around, but they have carbon rims which have the stiffness to stay round at low spoke counts.
It's not hard to explain - there is no good practical reason to have such a product. Mainstream race wheels are all factory built with much lower spoke counts, and general training wheels have to go on hubs which are almost exclusively made in 32h these days. The few boutique hubs made in other spoke counts are aimed at weight weenies who are likely to think any more than 24 spokes is a pointlessly large amount of steel to be dragging around, but they have carbon rims which have the stiffness to stay round at low spoke counts.