Imagine cooking: would a cook be better if he could taste his food only 3 weeks after he cooked it or would he learn better if he could taste it right away?
Another cooking analogy is whether you can taste it before it's served (preview an image before it is developed). If not, you'll probably work hard to understand what makes a dish taste right rather than relying on continuous sample tasting.
I don't mean to say there isn't a place for both. Instant preview is very useful for experimentation or when you lend your camera to someone else who might not know how to use it (common vacation or group photo situation).
The ability to take large quantities of pictures without additional costs is a different aspect of digital cameras. This has given more opportunity for those with more basic skills to get a decent shot, but the person who took the pictures may or may not learn something in the process. Lots of people just delete the bad ones without thinking "what made this bad and the other one good?"
After shooting digital P&S for a few years, I have been revisiting film and have been shooting 35mm and 120 on several different cameras (rangefinder, pinhole, SLR, twin-lens, etc). Having only 6 to 36 shots per roll (and paying $10 per roll for film + developing) has forced me to think much more before taking a picture and taught me to let go of the shots that sounded like a good idea, but just weren't going to work.
Having a better understanding of what makes a picture visually appealing, how the basic camera settings affect the outcome, and just thinking a bit before you click make someone a better photographer regardless of the type of camera. Whichever technique helps one to learn more is good for that person.