Yes, but this still "freezes" the VM when the user creates it, and I've got no tools to force the software running in it to be updated. It's important that boxes can be updated, not just reliably created.

As just one reason why, many developers need to set up complex test data. We have tools to help with that, but they take time to run and each team has their own needs, so some of them still have manual steps when creating a new dev server. These devs tend to re-use their servers until our company-wide max age. Others, to be fair, spin up a new machine for every branch, multiple times per day, and spinning up a new VM might not be burdensome for them.