I immediately thought that this was some kind of bug, surely Apple has this planned for the iPad as well right? Wrong. Craig Federighi explained on the podcast Waveform that widgets for the iPad will continue to be constrained.
I had the same reaction after installing the iPadOS 14 beta on my iPad Pro back in June. They never showed it in the keynote, but surely if you can full your iPhone home screen with widgets, you can do the some on the iPad, right? It has more room, and it's honestly where we expected this to come first, but it didn't (not this year, at least).
The widget situation on the iPad is slightly different from last year, but it's effectively the same: widgets sit on the left side of your main home screen and you can swipe up to see more of them. This is nice for sure, but it was nice last year, and it does feel a bit like iPad users got the short end of the stick for this awesome new feature.
I'm sure this was a matter of priorities and making the needed changes to the home screen to accomodate widgets just had to get deferred until later. I'd be really surprised if iPadOS 15 ships with the same widget situation as today.