Why many people when talking they like to say "you know"?

[Fabio]

why many people when talking they like to say "you know"????

[Prezbucky]

My old boss used "you know" instead of "uh" or a simple pause.

My old boss: Tom, you know, you're good at, you know, eating and, you know, drinking.

Average John American: Tom, uh, you're good at, uh, eating and, uh, drinking.
_________________
Billie Jean is not my lover. Hee.

[Martino]

"You know" is something we in the English department of our office call a filler. It's used to fill in the possible silence when grasping for words or thinking of what to say.

Aside from "you know," most English speakers use "like" and "uhm"/"uhh" to fill in silence. In the industry I'm in, though, fillers are a no-no.