You pretty much can't be good at Int, Wis, Dex - especially as almost everyone also wants a positive Con.
At the end of the day, the difference between an 8 or a 10 is bugger all. Hell the difference between 8 and 12 is pretty small, when it comes to making skill rolls.
If you want a character with good stealth, perception and Investigate then you need to have a rogue with Expertise in the right places.
The Ranger who is sacrificing something more important just to improve their results on Investigate rolls one in ten, or one in twenty times, is really not using resources rationally. (If they want to do it for character reasons then fine, but doing so just for the sake of finding traps is a poor choice - if you don't need Strength then put the points into Con, or to improving Wisdom - it'll be relevant far more often).
I don't know if there's some sort of applicable congitive bias, but for some reason people seem to think there's some vast gulf between 8 and 10. (Perhaps people have a tendency to overweight the difference between positive and negative when compared to two comparable positive numbers).