This Is the Police has been pushed back five days because publisher EuroVideo forgot to push an important button on Steam—the one that, in EuroVideo's own words, says that the game is "ready for final approval from Steam".
That whole process takes a few days, apparently, so having now (presumably) hit that button, we'll have to wait until August 2 for the game. Here's the full, contrite and rather embarrassed-sounding apology, taken from a news post on This Is the Police's Steam page:
"The reason for the delayed release was a mistake by us here at EuroVideo" the statement reads. "When releasing a game on Steam, you have to hit a button in Steamworks saying 'ready for final approval from Steam'. Steam then proceeds to check the game, and makes sure it complies with their quality standards. Usually this approval process takes 2-5 business days, and you can not release the game without passing it.
"We were responsible to hit that button and unfortunately we missed this window, as we realized it yesterday, i.e. too late for a July 28 release. We made a mistake and feel very sorry about it. Weappy [the developer] has nothing to do with this—it was just a personal mistake on our side.
"Again: we are really sorry about that".
The GOG and Humble versions of the game have been pushed back as well, not because EuroVideo forgot to push buttons there too, but so the releases are still simultaneous.
Predictably, the comments under that mea culpa are generally angry, incredulous or paranoid. If you were looking forward to the game, and you're currently boiling with rage, I'd suggest maybe getting some fresh air, or screaming into a paper bag, rather than adding to the pile-on.