GAC gives you three advantages in terms of deployment:
Today .Net framework has only one system GAC. It is required to have Admin privilege to update GAC.
People like what GAC offers. But you can’t take advantage of GAC if you don’t have Admin privilege. A natural ask is, can we have per-user GAC so that we can have all the advantages of GAC without the restriction of Admin privilege?
The ask is very reasonable. The problem is, when you add per-user GAC to the picture, the deployment model becomes much more complicated.
From a model’s view, Per-User GAC defeats many benefits of GAC. Whether it will be in future version of .Net framework will remain to be seen.