Technically that is discrimination. Discrimination applies any time two different groups get two different outcomes. It's a term that is used in economics without the negative connotation of things like racial discrimination.
Senior discount at the diner? That is literally called price discrimination, look it up.
I find this interesting for several reasons. I've lived in 5 countries. America is the only country where I've seen the senior/veteran/police/whatever discounts trotted out.
Isn't it funny, however, that "we" claim to value seniors, but almost to a man, elderly mom and dad are tossed into care homes as soon as it's inconvenient for their adult kids. Sadly, this is done for many reasons, many of which are to bilk people for their money. Most countries bring mom and dad or surviving parent into the home for the remainder of their natural life. In other cultures, not doing so is tantamount to an anathema. Welcome to America, land of the free to be bilked, and home of the brave should you step foot into hospital.
Senior discount at the diner? That is literally called price discrimination, look it up.