Earlier quoted context omitted.
Because it's not about "tokens", it's about "I want a Coke and I have a nickel right now and want to give you that for a Coke". Impulse buyers don't buy rolls of tokens, especially not when $1.50 in 1935 is actually worth about $26 in today's dollars.
Think about how many people use real, actually-issued, legal-tender $2 bills, then think about whether a $0.075 coin would have promoted impulse purchases. Now think about freemium mobile games. The games that price their in-game purchases in a separate currency make more money than those that price their micropurchases in the user's native currency. People are less apt to make impulse purchases with real money. But…
The tokens you're suggesting sound like sort of a precursor to today's gift cards. Coke would certainly have been making money on tokens purchased but not spent.