Hardware support will heavily decrease and no one will be able to make it work for unsupported kernel versions(just as with nvidia, esp. see nvidia optimus zero linux support). Aaand because of still-low linux desktop presence, barely ANY hardware vendor will join.
With non-supported kodak printer, the end argumentation was like - we invested much in windows and linux does not have this, and we feel like zero to improve it to our taste, so no support. Still they managed to release Mac driver. Which means they simply lie and simply dont care, regardless how open or closed the state is.
And if I read correctly, most of time when a blob got reverse-engineered, hackers discovered it being released as a blob for only one reason - very stupid implementation.