And with nearly all other games you get patches whether or not you bought a new or used copy. Wake up.
Valve uses excessive DRM. They could, if they wanted to, disable every single Steam game in existence.
In regards to your first point, while true to an extent, this is Stardock's method of discouraging piracy of their products. You buy a retail copy brand new, you get the code, and you get the support of the patches once you prove your purchase by inputting the code. Pirates don't get any updates as they would have to steal a new retail copy to get the code, and if they're to go to that extent, they may as well purchase it.
Here's the thing, it's frustrating, but have you ever dealt with something worse, such as SecuROM? You think tying a code to an account and barring you from updates is bad? Try a limitation of three installations, per computer. Sure, you get an infinite amount on one computer, but change the hardware, and it takes up another installation. In Stardock's setup, you can still play the game regardless of how many computers you install it on or how often you alter your hardware (i.e. upgrade it), you just don't have access to multiplayer or the updates. In that scenario, which do you find yourself preferring?
As to the latter point, while that may be true, at least you don't have the hassle of the above example. They don't limit your installations, you can play the games that are single-player offline (despite what some may say, Steam does have an offline mode which allows it), and for the most part you're free to do with it as you please.