Online players (like myself) play 4-20 tables at the same time, there is NO chance you can keep notes and ranges yourself at all those tables against all 6/9 opponnents at the same time.
So that's why we use HUD to keep track of it.
Now in a live game, you're at a table with 5-9 other players, that's not an awful lot. Now there are some real life help "programs" (including a notepad, maybe the notepad on a mobile device, and I know there are
Apps that can keep track of VPIP/PFR/3bet and such, you just have to put them in yourself, but you have way more time for that live.)
Just look around the next time you're in casino, and look how many young guys you'll see with their mobile device, their probably not texting all the time.
Anyway, you play less
hands with less opponnents so you have way more time to observe them,
And obviously you won't know their exact flop afq or their turn c-bet%, but even online I don't use those all the time, only in some big decisions.