One word. Why?
This is something that people with a lot of money to waste find interesting. I have limited space in my gunsafe and every single firearm there is useful and of top quality. Every single one also puts rounds downrange. I own zero safe queens.
Because some people want an SBR-equivalent without the $200 tax stamp, the 9 month wait or the registration of their firearm. AR pistols with braces are a solid alternative to the painful SBR process and, should SHTF, can be readily swapped with a real stock.
The historical provenance is what interests me, more than anything else.