Hmm, I'm probably going to regret getting involved in this but here goes..........
The Park's, Morris's, Dunn's etc did indeed use caddies for important matches but I've seen nothing to substantiate the notion that they used caddies for bounce games or practice rounds and these were the very best. The average professional in the latter part of the 19th century certainly wasn't flush with cash so the notion they took a caddy every time they went out to play is fanciful. After all, they also made money out of caddying so are they going to pay for a caddy, after they themselves have toiled to earn the same amount of money ?
The use of caddies was mainly restricted to the better off who could afford it. The hoi polloi meanwhile got by without, and yes the common people did indeed play golf back in the day.
At the main golfing centres such as St Andrews, Musselburgh and North Berwick, a large portion (probably the largest portion) of the caddies were made up of children. At other golfing centres it was nearly all children. Some of those children did play golf and became professionals but they didn't learn the game by carrying clubs for some old retired colonel but by actually playing about themselves. The reason they caddied wasn't to learn but to earn. It was that simple.
There was no need to caddy to be introduced into the game and that is very much the case today. As much as it has been romanticised and stories often repeated of Big Crawford, Fiery and the like, caddying has never been anything other than a luxury for the better off.
Niall