It used to be normal in the U.S. to walk people to the gate until 9/11.

Now you can escort someone to the check-in counter and up to the security checkpoint, and meet people at the luggage area to help with bags.

But in practice it seems rare to do so if there isn’t a particular reason, probably because you’d have to pay to park or ride transit and it’s usually a trek beyond that. Honestly if they allowed you to go through security with the passenger and wait at the gate, I’m not sure how many people would even do it here (or how many passengers would want their loved ones to do so).