Yes, "rookie card" is a hobby invention. But at the time, not an unreasonable one.
And it was around at least a few years before 1980.
The reasons they were worth more were
The general human obsession with things that are "first"
Before the mid-late 70's maybe a touch earlier, most cards were bought by kids. And most kids only collected for 3-4 years. At the time, many players didn't become stars right away. So the chances of having a players first card were fairly slim, and the chances of that card surviving the new hobby/mom cleaning/interest in cars/girls/ move to college .....were poor.
Using the 54 Aaron as an example, if you got one, which card went in the spokes? The established star? Favorite player? Local hero? Or that kid in Milwaukee who hit 13 homers? And if 54 was the last year you were into cards, it likely got tossed with the rest of the collection a few years later.
So yes, there's a reason rookie cards especially in better condition are worth more.
Calling the 52 Mantle a "rookie card" is generally ignorant. I have a hard time taking someone seriously if they call it that. Especially dealers.
The 52 Mantle is the most overhyped double printed card of a great but somewhat hyped player in a regional market that thrives on hype. (Any questions how I rate the card?
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