And makes it more expensive. There is the seen benefit and then the unseen cost. Every game released will have to account for the possibility of it, and will create issues for people who really didn't want those issues. After awhile people will forget there are associated issues and costs, but they will still be there.
Putting on my Pollyanna hat...
Or it could make it a lot cheaper, if the server were developed entirely on open-source infrastructure from the start. Hopefully the actual game logic would be developed entirely in-house, making it easier to audit before releasing.
If you plan for it from the start, it's a small cost. And the simpler the game development process the cheaper it gets.
Middle ground could be completely open API from the start, so community could build alternative server from the ground up.
Not everything that makes a product more expensive to release is the end of the world.
Every game released whose developers have chosen to complicate its design with a client-server architecture. It's not like this is going to hurt the little three-man teams making games on shoe-string budgets. Yeah, it's going to make big budget games a little more expensive, just like how cars with seatbelts are a little more expensive to build, and like how it's a little more expensive to do proper waste management instead of dumping sludge into a river.