@Edinson113 Because Kevin Feige doesn't actually care about long lasting stakes or things making sense. And he's never cared about any of the shows except Daredevil and only because of its acclaim.
The reason why Runaways and SHIELD ignore the Snap is because:
1: Feige allowed Christopher Markus & Stephen McFeely to have the Snap last 5 years and be a permanent part of history (instead of erasing it from history which is what they should have done)
2: The writers didn't know that was going to happen. Feige couldn't be bothered to tell Jeph Loeb or any of the TV show show runners about this development, because as far as he was concerned, those shows didn't matter.
But the main reason is because Feige wanted to have his cake and eat it too. He wanted the brownie points of having a jaw-dropping game-changing event in Infinity War & Endgame, but he also wanted to continue business as usual.
Thus, he allows the Snap to happen -- and then allows everyone - even under his own watch - to ignore or downplay the Snap, so that business can continue as usual. It's a very typical and cynical approach to shared storytelling.
I don't think Feige or Markus or McFeely realize or care just how devastating losing 50% of the population - and then gaining it back - would be on society. The world would be an unrecognizable pile of chaos.
Instead, we have people occasionally mentioning it, or not mentioning it at all, and society functioning normally. If that's the world Feige wanted, then he should have only had them erase 5% or 2% of the population. That way, you can still have your jaw-dropping tragedy, but society can still function. 2% of the population is still devastating.
On top of that, most of the characters in the new movies and shows didn't even Blip. The Blip didn't affect their lives at all, so it might as well not have even happened.
The Eternals were exempt from the Blip and all it did was delay the Emergence.
Neither Shang-Chi, Xialing, nor Wenwu Blipped. Their lives were unaffected.
Neither Steven/Marc, Layla, nor Harrow appear to have Blipped. It might as well not have happened.
Neither Kate Bishop, her mother, Echo, or Kingpin Blipped (Kate had to survive so she could grow to be a 20 year old).
The only characters who were confirmed to have Blipped were characters from the movies who we already know Blipped like Spider-Man, Falcon, Bucky, Wanda, Hawkeye's family, etc.
The stories that were most affected by the Blip were WandaVision, Falcon, & Far From Home, and even there, the Blip's impact was weak sauce at best, with Falcon being the only show to even attempt to show any global political ramifications.
And it's because it doesn't matter to them. They wanted to wow the audience with the fact that they did it, and then treat everything like the way it was before Infinity War, because that's more convenient for new writers and their "creative freedom." Never mind continuity or consequences.