Training classes are limited by the number of system in the classroom. After each training class all the system need to be rebuilt to get back to the same starting baseline. This is also true when a new version is released or if the classroom has to support multiple products.
By deploying in the cloud space, there is much more capacity elasticity. And resource are only consumed when systems are deployed. Updating a system design takes minutes and multiple designs can be saved in the library to cover different products or versions.