Why every Lee Sin is now building damage?

Most Lee Sins that I encounter on battles are not building that traditional build of Warrior then full tank (sometimes with a Hexdrinker)

Most Lee Sins are now building damage, with Last Whisper, Ravenous Hydra, and even Black Cleaver as their damage items.

Have people realized that if you build damage on Lee Sin you can actually become a threat? I mean... I know that some tankyness is necessary on Lee Sin (such as Randuin's Omen) but without damage items Lee Sin becomes a very poor tank late game as he doesn't have a lot of utility and usually all he can do is to displace enemies with his ultimate, since his attack speed slow has been removed. But with actual armor penetration/lifesteal items, Lee Sin is a monster. He has almost as much burst, sometimes even superior burst to some assassins, yet is tankier and has more mobility than most of them. He can one-shot any squishy and take out more than half of a tanky champion's HP.