It's be good to be able to restore a snapshot to an existing instance, so that a restore wouldn't change the IP address. An IP may be more or less dispersed among clients. Now after a snapshot restore, which requires a new instance with different IP, those clients are affected and have to be updated.
Yes, in a development environment the number of clients wouldn't be large, but still, there's inconvenience in saying, "Oops, let's roll this server back to the last snapshot" that would be eliminated if the IP were unchanged.
I may be overlooking something, in which case I'd appreciate any insight.