They're only doing the "right" thing because they have no choice. They couldn't pump enough money into third party development to make up for the ill will they'd garnered with this exclusivity DRM, especially not with companies like Valve doing the complete opposite -- giving money to third party devs with no exclusivity deals whatsoever.
Turns out some developers can't be bought[1]. Who'da thunk it?
1. https://www.reddit.com/r/Vive/comments/4nxpnq/fuck_facebook_... (For the sake of fairness, it was a time-limited exclusivity offer that was made to the Serious Sam devs, but an exclusivity offer nonetheless.)