I'm sure larger scores were for wow factor, to draw in the player at first. Most people probably associate "millions" with becoming really large numbers in general...

But there is a balance there - I really dislike the billions scoring games, as well as the JJP-level thousands scoring games.

Millions for jackpots, getting up to 10s of millions for really special super or multiplied jackpots, and games totaling 100-200 ish million point being solid scores, seems like the sweet spot to me. Playing a full game on a modern pin like the Hobbit and only scoring 100k points feels pointless. Yet that scales right up to be an equivalent score range. As long as the scoring is balanced it shouldn't matter, but it does...