Indeed they do, however companies like Meta (altruistically or not) are preventing OpenAI from building 'moats' by releasing models and architecture details in a very public way.
Meta is already capable of monetizing content generated by the models: these models complement their business and they could not care less which model you're using to earn them advertising dollars, as long as you keep the (preferably high quality) content coming.
At which point the new underdogs would have an interest in doing to them what they're doing to OpenAI.
Assuming progress for LLMs continues at a rapid pace for an extended period of time. It's not implausible that they'll get to a certain level past which non-trivial progress is hard, and if there is an open source model at that level there isn't going to be a moat.