Before I get started: Last week I equated Impulse with the other digital delivery system tray squatters. But it's worth noting that Impulse doesn't do this. Once you've downloaded the game, you can close Impulse and it will not shoehorn itself into the proceedings. It's worth checking out if you're one of the people looking for a less restrictive alternative to Steam.
Just to keep this article from getting out of hand, I'm going to completely ignore piracy as an issue. We've only got so much space to spend here, and dragging piracy into this will make this whole discussion that much more complicated. Besides, it's not like I haven't already beaten that horse into a fine paste.
Developers and publishers have been working on various techniques for getting people to pony up for their single-player game instead of borrowing or buying used. Ideally, they want everyone who plays the game to pay full price for it. There are two different approaches for doing this. One technique has been widely praised as a pro-consumer policy, and the other has been denigrated as a cynical and short-sighted idea. Let's look at the good one first:
For years Stardock has been putting out solid games and then refining and expanding the game after release. They take the initial feedback from the community and use those suggestions to guide their efforts. Stardock will then release regular patches that tighten up the gameplay and give the audience more of what they love. But these patches are only made available to people who have registered the game and linked the serial number to their account. If you get the game on loan from a friend or buy a second-hand copy, then the updates won't be available to you. (Again, we're ignoring piracy today.)
The upshot is that the game in the box is yours forever, and the post-release extras are there to reward people for buying the game new. Unlike DRM with online activation, you'll never lose the original product. If Stardock president Brad Wardell cleaned out the company bank account and took off for the beach and the Stardock servers went down, my boxed copy of Galactic Civilizations II would keep working. I might lose the updates if I didn't make backups, but I'll always have access to the game I paid for as it existed on release day. It's mine and it will stay mine as long as I take care of the disc. The post-release patches are gravy.