It's a lovely idea but in realistic terms the market for selling a Kemper stomp is limited to only Kemper users, which is a tiny proportion of the guitar market, reduced even further by the number of users who would pay out for a simulation of a pedal when their is a heap built in from factory. Like all companies in these days of their resources aren't unlimited and would almost certainly be better spent developing gear that isn't limited to a relatively small market.
The market doesn't have to be small. The core of the code would be the same for all (whether it is a hardware pedal or a plugin). Only the interface with the host would differ. The host could be Kemper, but also Logic, Cubase, etc. Maybe also Helix etc.