Is this because they are afraid of the model misused, like used for generating fake reviews? It is frustrating that I've been hearing great news on NLP but am able to try none of them myself.
It's because the model weights are the valuable thing here. The fancy new architectures are nice and everything, but transformer models are a dime a dozen these days. Seems like they're using this as an example to point at and say "Hey, look at us, we support open source!", whereas unless you're willing to go ahead and spend a small fortune on compute (possibly using their GPUs), these models are somewhat useless.