If they programmed it correctly, migration to a new server would involve "rsync *.tar.gz . && tar xfz *.tar.gz" or something similar. There is no reason that needs to be complicated, so maintenance time should be minimal.
Yeah, good luck finding *anything* that's that simple.
Even moving the simplest possible website (just static files, nothing dynamic) to a new host is more work than that. (You could move the content itself with rsync or tar (though not with the command lines you gave), but the new server needs to be configured, the web server still needs to be set up, etc.)
If your definition of "programmed correctly" is that migration to a new host is as simple as you think it is, let me give you a hint ... by that definition, almost nothing of any value is programmed correctly. And modern systems, with clustered setups with failover across multiple nodes, multiple databases, connections to billing systems and the like are several orders of magnitude more complicated than you seem to think they should be.
In any event, this is moot. It's Gamespy that's shutting down, not some server that EA runs that's currently sitting under somebody's desk. In order to fix this, EA would need to dig the source for their old games out of storage, make sure they can still build it (for a game that hasn't been touched in a decade by them, this is real concern), pay a programmer to replace the bits that Gamespy uses to use something else, build it, run it through some minimal testing and release it. All this for a game that may not have made EA any money in years, and it needs to be repeated for a large number of older games.
It's a business decision. To update every game ever made by them would cost a bunch, so EA is wisely deciding to only support the more recent games or the games with sufficient demand. We could argue that they're not using the ideal criteria in deciding what should be updated, but ultimately they do have to draw the line somewhere.
My guess is that Gamespy has had very little development done in a long time and mostly just sits in a room of servers somewhere mostly running on autopilot -- costing money in hosting and power costs. I'm not sure how it is about making money -- do game publishers pay to use it? Advertising? In any event, if it's costing money but not making money, they probably told the developers if they didn't pay up they'd shut it down, and the developers didn't pay up sufficiently, so ... shut it down.