Unlike other mediums, be it television or movies, developers and publishers using little white lies to sell products has become the norm in video games. In their defence, saying one thing and doing another isn't always their fault, and the constantly shifting nature of game development means ideas change, targets can't be hit and features are cut entirely and saved for the sequel.
Likewise, fans by now should know to take everything they see at press events like E3 with a pinch of salt, as the demos shown off are often a reflection of what the studios hope their games will end up looking like, rather than what they currently are.
Still, while a lot of that is excusable, it's a different beast entirely when developers straight up lie to your face, promising you one thing and delivering something entirely different. The bait-and-switch tactic can be used to good effect - see Metal Gear Solid 2 or Avengers: Infinity War for an example from another medium - but more often than not it's used to fool you into buying a game that sounds far better than it actually is.