Can you back this up with evidence? I have always thought they were implemented to slow you down so that you don't rush through the game "too quickly."
I cannot, in part because I can't find the article which originally made the assertion. But it's more of a philosophy for you to test for yourself the next time you are playing through one of the older RPGs, examine your motives for playing and see if you agree with it.
Using the example of Dragon Quest, I remember that the game progression wasn't based on EXP so much as it was based on gold. My exact frame of mind for playing through the game went something like this:
> So I found a new town. The blacksmith there is selling this awesome new chainmail armor that I totally want, but I don't nearly have enough gold for it. Guess I'll come back later. (Here is the typical strive for greater strength which is characteristic of RPGs)
> Hmm. The monsters around here are not dropping nearly enough gold; it's going to take me years to buy that armor at this rate. I wonder if there are any tougher monsters I can be fighting to make this process go faster? (And thus, I am driven forward to find new parts of the game)
Your mileage may vary, but the philosophy seems to agree with my own personal experiences.
Don't most games these days fuck it up and have it so that by the time you get enough money for the gear you'll have already stumbled upon a new town/shop with yet even better gear? Or while gold farming you'll have leveled up enough to no longer need that gear to get past the point your currently stuck at?