Reasons : there is a significant amount of work needed to get codes to work on a distributed hybrid or gpu-only fashion. It's a completely different coding paradigm that needs significant studies before commercial entities adopt gpu use at scale. All-gpu solvers are starting to be developed, such as fun3d GPU[0], but features are very limited. GPU development is starting to catch up in the community, so it won't be long before a significant portion can operate heterogeneously or in gpu-only mode.
Forget side-loading, the fact that I can't develop and run my own applications on iOS without having to ask apple for permission every week is infuriating.
[0] https://fun3d.larc.nasa.gov/GPU_March_2021.pdf