I think the reason why most adults lie like 5-year-olds is because inventing a professional lie takes a lot of detailed thought which is hard work. But most people are lazy. It's as simple as that.
True that people tend to lazy, but I'd more attribute that laziness to the audience of public liars, perhaps moreso that people like their ears tickled, want to believe what they want to believe, instead of truth. Politicians, with all the money thrown at them and campaign workers, lined up around the block, tell some of the dumbest lies. Criminal defense lawyers strain to find "intelligent" lies. It's not that easy to tell "good" lies, since one has to make something of nothing, make it look congruous with truth, have no holes such that the lie holds up to scrutiny, which, in fact, is near impossible.
I've always thought the problem more, again, people hearing what they want to hear, often the lies appealing to their narcissism, prejudices or greed, lies an objective, analytical person would find stupid, yet they'll choose to believe. It's incredible, financial con men, how people will so throw caution, simple, common sense, due diligence, out the door, for empty lies. They'll throw money at con men that merely appeal to their greed, without a thought to the fact they're turning over what amounts to a power of attorney to somebody they don't even know, by investing "with" them, allowing their complete control, in turn allowing the cons to simply pocket the investment, that's never invested, at all. (Note the "genius" con men windup in prison, too, often for decades.) The cons will have these seminars, free lunches, where they do this pitch, invest at no risk, triple market returns, etc. It's stupid as all hades. If there were a scintilla truth in their investing secrets, it would be a secret for about five minutes: all Wall Street would be making their riskless, high returns. It's dumb, dumb, dumb, doesn't hold up to common sense, yet people will throw tens of millions of dollars at them. They don't really even know the pitchman isn't a criminal, and they very often have criminal records! Are you going to throw a half a million dollars at somebody to control, who gave you a free lunch and some pie-in-the-sky spiel, and not even do a ten dollar background check? Well, it happens all the time. The lies are dumb, it's just the audience is dumber, corrupt in their own way, really.
The same with politicians. They run these ads, full of pabulum, that they'll go to the lousy House, cleanup Washington, will eliminate waste, give everybody everything for free, at no cost to anybody (except a handful of ultra rich people you're programmed to envy to hatred, because, in fact, you're more covetous, and this despite very fuzzy math even they don't have trillions to spare to make all that silliness work), ads how they'll single-handedly make the nation that shining light on the hill, then the entire world, one can only suppose, because nobody else has ever been good like them, especially their opponent, and, oh, they like puppy dogs and babies. I don't know about you, but I've seen that silly rot all my life in campaign ads, then watched them go to Washington and fill their pockets to bulging, as the same old bribed creatures of K Street, proof in the pudding that neither has anything really changed, ever. But it works, over and over.
No, I think it's more people are evil and dumb, love the lie, and maybe a lot of lies are stupid because the liars are stupid. At least you can't say they don't have a whole battery of people, working on their silly lies, and all they get from it is some campaign ad for the brain dead, one can only conclude. Scariest thing about the human race is how that works, every time.
There is none so blind as those who will not see,
Jeremiah 5:21-23 Hear now this, O foolish people, and without understanding; which have eyes, and see not; which have ears, and hear not: Fear ye not me? saith the LORD: will ye not tremble at my presence, which have placed the sand for the bound of the sea by a perpetual decree, that it cannot pass it: and though the waves thereof toss themselves, yet can they not prevail; though they roar, yet can they not pass over it? But this people hath a revolting and a rebellious heart; they are revolted and gone.
