@Romagia:
A trait doesn't have to make the sim do some random animation once in a while to make it not low impact. Yes, some traits affect things more than others, what we are listing here is those traits that don't change the daily routine of the sim, the speed it learns, how well it relates to other sims, or even give a noticeable (good or bad) moodlet or boost any particular lifetime wish.
Most of what you mentioned and i refuted either offer a new way for a sim to play (mooch), boost a particular lifetime wish, offer a noticeable moodlet or let your sim build up relationships better with other sims.
Compare to, say, never nude, and you'll see why most of those, while lesser/unpopular than other traits, don't really make it to the top 5.
About hidden traits:
The trait unlocker lets you pick them like normal traits, limited by the standard game interface. Basically, it removes the hidden attribute of the traits. Normally, they don't appear on the list, don't take up a slot, and can only be obtained through genetics (this may not be true for the culture traits, need to confirm). You also don't know you have them until you, say, realize your adult sim can sneak or that your sim is not dying during a fire.
Hidden traits have lesser effects than normal traits, they're extra, "collectible" stuff to acquire for your legacy games through playing mad breeder with your sims.