Do they really miss them or do they decide not to call them?
Statistical evidence shows that referees will usually call a penalty against the team which did not receive the previous penalty. It's also proven statistically that the amount of time left in the game and score strongly influences whether a penalty will be called or ignored. It's not that the refs don't see the penalties, it's that their bias prevents them from calling it.
The evidence was compiled for a master's thesis several years ago. Refs are proven to be biased.
Of course refs are biased. So are you. So are all humans
For anyone who hasn't reffed a hockey game, I suggest you try it sometime. As someone who has officiated from novice hockey up to beer league, I can tell.you that there isn't one game where I thought "wow, that was easy"
The reality is that hockey refs are taught "game management" at the upper levels of certification. As the instructior of my level 3 clinic explained it... "reffing a hockey game is like holding a bird. Do it too tightly and you kill it. Do it too loosely, and it gets away from you"
What he meant by this is that ypu CAN'T call every single thing that fits the definition of an infraction. It would mean a constant parade to the penalty box for both teams. Instead, you need a threshold... for example... if it causes a loss of possession of the puck, it's an automatic call. If someone's stuck gets in a player's hands, it's automatic, etc
From there, the most important thing is consistency (something that you may be alluding to). Nothing drives coaches and players crazier than when something that is a call in the first period isn't one in the third. That said, I think lots of refs (for better or worse) put away their whistles late in a game because they don't want a calldo determine the outcome of a game. They justify non-calls at that juncture by having it go both ways. As in "yeah, that was a slash in the first but I'm not calling it now... but I'm not gonna call it on the other team either so it's all good". In fact, my junior hockey coach referred to the last 2 minutes in games we were up as "tackle time" because anything short of assault wasn't getting called. And even that wasn't sometimes lol
So sure, some nerd did a thesis on hockey officiating. Great. They probably don't understand the feel and flow of the game, as well as unwritten rules and codes that both players and refs use to navigate them. Most casual fans don't either, so the frustration is understandable