They could make it optional, but having such a technical option wouldn't be Apple's style. Perhaps it could generate a new random MAC address for each saved network, which would be thrown away when you use the 'Forget network' command.
Yes, I do this at home because it resolves the problem of a duplicate IP addresses on the network caused by a device assuming it still has the same IP address (Apple devices seems to do this in particular) while meanwhile another one has taken it.
There's been plenty of debate about whether this rapid DHCP behavior is desirable (e.g. Is the improvement in user experience worth the potential for conflicts and/or other issues on networks not expecting this?), but, either way, I don't see how that behavior can be fairly characterized as polite.
My experience is I get home, open my laptop, and it seems to by default assume it has the same IP as last time it was on my home network. Meanwhile my kid's 2DS game is using that IP, and I have a few minutes of chaos. I just assign fixed IPs to all the regularly connected devices and I don't encounter that.
Are you sure this isn't a router problem? A number of routers have an issue where they occasionally drop their table of DHCP allocations and just start again; this mostly only manifests when a new device connects.
