Presumably, they want to get everyone used to their environment so that when their hardware lead doesn't mean as much in the future, there will be hesitation to leave. We know they aren't currently doing anything untoward as there is plenty of overlap between paranoid tech experts and people interested in pioneering new tech. Can't hide from them. The software and network traffic has been thouroughly vetted and everything is so far doing exactly what it would need to or purports to do.

As long as you go into it knowing you will be changing platforms at some point in the future and hedge all software purchases against that in your mind, the only remaining downside is whether you can stomache giving them your money.

And if that ever changes, it won't go hidden.

There is also something to be said for the fact that everyone in the Meta community see VR as thriving and growing, and everyone that is outside of it sees VR as stagnating or shrinking. So their money is doing that too presumably.

Their ultimate main goal is also, of course, marrying the tech from VR headsets to the tech from AR glasses. Which will be a true ubiquitous product. Being the first one there will be a huge pay day.