The thing is, it's much harder to implement "vendor lock-in" for RPGs than it is for hardware or software which has business uses. The cost of switching to another RPG system is very low: all it takes for a group of friends to start a new RPG is for the geekiest of them to buy a rulebook and evangelize it, there's almost zero cost (but the rulebook(s), of course).
I find videogames are a red herring as an argument for D&D, since most people playing CRPGs based on D&D don't even need to understand the rules; the computer does everything for them. And people will buy a flashy CRPG regardless of the underlying engine, all that matters is that the game is fun, hyped, has nice graphics, and friends are playing.
IMHO WotC is pursuing a double strategy. On one side they try to pull a marvel, meaning becoming big in the media industry with movies, series and videogame (I expect to see many D& D games in the future if the movie is successful). On the other side they will try to create a subscription based walled garden in the RPG world.
you're right that for the moment switching to a new system isn't really expensive, it may change if wotc manage to create this walled garden
As for the OGL license, you have to understand that ttrpg companies are usually very small (some people, sometimes only one) so they can't really spend a lot on exploring what is the best license or publicize a new one. So they take the license that is the most used in their domain which is the OGL