They actually do this on a lot of the oldest devices, but probably not for the same reasoning. I occasionally come across phones that are too old to support Google Play Services (<2.2 IIRC), so they're stuck on the Android Market, which no longer works.
It would seem that's not made OEMs/Carries feel the need to update them.
Are you sure? I think that the Android Market on 1.6 (ADP1) still works.
Perhaps the dev phone has a slightly different situation? I know someone with a 1st generation HTC Wildfire (formerly) for testing and when you the market throws a connection error and refuses to go any further. I've seen the same thing on other Android phones from that era.
I'd like to think so but it seems equally likely that carriers would either push you towards their own stores or tell you that you need to buy a new phone if the message was anything less aggressive than “There is a critical security available which must be installed before using the web. Please contact your carrier to ask for it”