This is because for whatever reason, Apple’s 96W USB-C power adapter designed for the MacBook Pro is currently out of stock and according to Apple’s website, customers might have to wait 2-3 months before it arrives. As MacRumors notes, in Japan the shortage is said to have started as early as August, and now it looks like it has affected other countries around the world.
It is unclear why that is, but it is possible that the global chip shortage could have a role to play in the delay. Alternatively, there are rumors that Apple is launching new MacBook Pros next month and some have speculated that we could see the return of MagSafe, so maybe Apple is clearing out existing inventory.
You could always use third-party chargers but that’s generally not advised, so until we figure out what’s behind the delay, you might want to take extra care of that charger because it might be hard to replace in the next few months.