Your comments in this post and others seem to indicate that the players will always catch on (or at least you will), but that's not true in my experience.
No. I won't catch on to all clues. Probably not even half. As a player, I don't necessarily hang onto every word of the DM and analyze it for hints. I'm too busy having fun making jokes and other Tom foolery. You might find me a disruptive player. And I will make mistakes. I make mistakes all of the time. On the other hand, I will rarely face palm like you have stated. If you were my DM and gave us some foreshadowing 3 weeks earlier, I won't remember it. I barely remember the highlights of a session from 3 weeks ago, let alone subtle foreshadowing. Even when the other players or you as DM talk about it, I'll probably just shrug. If it wasn't important enough at the time to take note of it, I won't remember it. All of the DM's hard work wasted on a player like me.
I'll telegraph the pit trap. If you don't need the clues, then it shouldn't be a problem for you that I do that, right?
I guess you are missing my point. I wouldn't want clues every time there is a trap in the room. That's NOT fun (or at least for me). Like I mentioned earlier, if you are going to spoon feed the players with clues on every threat, you might as well just play their PCs for them.
Balance. Sometimes the DM does it. Sometimes the DM does not. If he does it all of the time, I might as well play Monopoly for all of the real decision making the DM is giving me. It feels artificial. PCs should not be psychic. Yes, you can couch it as the environment giving them information, but most PCs should not be Sherlock Holmes-like.
And btw, I'm glad this works at your table. Different styles for different groups. I have played in a few groups that I have quit after a few sessions because DMs did stuff or had house rules that were just too uncomfortable (sometimes other players were an issue, but usually these types of incompatibilities are driven by DMs).
Telegraphing, foreshadowing, and the like isn't about the DM protecting the character. It's about providing the players with enough information to make meaningful, informed decisions in fair challenges in order to reduce randomness and have control over their destinies. A great deal of experience in this regard has shown that they don't always make the best decisions even when informed. So there is your balance right there.
It might not be about protecting the characters, but it does seem to be a little bit about controlling the characters. Sure, they will make mistakes or not get every clue. But the clues you do often supply are a type of railroad on the adventure, possibly without you even realizing it. DMs have a HUGE amount of influence in a game and the more hints a DM gives, the more players are going to be inclined to follow the DM's lead. As a player, I don't want the DM giving too many hints because I will be outvoted at the table in decision making 10 times out of 10 by the 3 players who do want to always follow the DM's hints (even if they are misinterpreting them).
A DM should be impartial and him giving out too many hints, regardless of how they are couched, is the opposite of that.
And yes, I understand your POV. You just do not seem to understand mine. I want gotchas (not deadly ones, but challenging ones) a fair portion of the time because otherwise, the game is too predictable, or at least the portions of the game where I pick up on the DM clues. And even if I do not pick up on a clue, some other player might and again, it has the appearance that the DM is leading the party instead of the players.
Read the Instigating player on page 6 of the DMG.