My father traveled quite a bit when I was younger. It was a fundamental part of his job, something he couldn’t avoid. It lead to some pretty cool family vacations, so we learned to deal with him being gone now and then.
He spent a bunch of time flying on TWA, and then American Airlines after AA acquired TWA out of bankruptcy. He had colleagues that traveled a lot more than him and received luxurious gifts like luggage and crystal for hitting milestones in the amount of flying they did with the various airlines.
Back then, my father recalls getting upgrades on virtually every TWA flight he flew, regardless of the destination. He can also remember when he transitioned to American Airlines that he would receive upgrades on flights to London even as a Gold member purchasing coach tickets.