“So” I think they use “so” as a verbal tick that acts as an attention-getter, as if they’re summing up all of creation up to this point, to make their statement.
Yes, most common in Millenials, who of course feel entitled to immediate importance.
It may also be a DC-area thing, but that’s all I know.
“So...” = Fingernails on chalkboard
Fingernails on Chalkboard... Abso-freaking-lutely!