Vegetables

I was writing about cooking squash at my own site yesterday and it occurred to me that the selection of fresh vegetables in supermarkets today is vastly superior to what was around when I was a kid. Carrots, celery, iceberg lettuce, a bell pepper maybe - I can remember see those in the stores. Asparagus, spinach, turnips - those I don't remember ever seeing during trips to the grocery. Heck I can get cactus right down the street if I wanted.

First is it true there is a better selection now? Maybe, like so many, I grew up in a veggie-free home so if it didn't come from a can, I never saw it.
If it is true we do have more choice in vegetables today is it because of technology like better refrigeration or more effective pest control? Is it due to improved logistics? Maybe there's just a bigger market now for fresh food. My theory is NAFTA had a bit to do with it. It's been over a decade since it was signed, does anyone remember how the grocery shelves were stocked way back then?