The top end OEM models from each brand already run internal bypass in the shocks. Plus you then enter, cost, packaging, and the general market consumer would have to understand how to adjust & tune, which is the last thing a OEM wants the customer to play with. This is also why the electronic adjustable shocks by a switch on the dash is a better way to give the customer 3 standard settings.
In the Score Open UTV class you can run two shocks per wheel and the Newline chassis have been running two in the rear, and a slaper hydro bump stop off the upper front arms. The cars have yet to beat the Factory Polaris cars which are still running a single shock package.