So why not just get it ready and then only launch it? According to Gurman, there are several reasons why the headset could launch potentially later than 2022. One of the reasons is because Apple would need to work with various partners and governments globally over things like prescription lenses and also work with partners to ship components that neither side have shipped before.
As to why Apple plans to announce it first before releasing it, this is due to leaks. In this day and age, seeing products leaked ahead of launch is becoming increasingly common. To avoid their product being leaked and having competitors steal the idea before it’s officially announced, Apple would announce it first before making it available later.
It is unclear how long it would take in between the announcement and launch, it has been suggested it could take as long as the original Apple Watch. According to Gurman, the OG Apple Watch took 227 days to actually launch from its time of announcement, so it is possible that the device could be announced in 2022, but it might only be in 2023 that it could become available to purchase.