First, it really speeds up my prep time when I'm rushing to serve dinner. Open jar, dump in casserole dish, add starch/vegetable/sauce or spices, and heat. Viola, dinner is served.
Second, I can buy the cheapest cuts of meat. Pressure canning makes every meat I've processed deliciously tender and juicy. No more tough beef or chewy chicken.
Third, I can take advantage of bulk buys. Post-holiday sales on whole turkey and ham, the roll of ground beef from the discount store that's the size of my leg, the giant food-service pack of chicken parts, etc, all of which cost less per pound? Dump it into my biggest crockpot, cook it until it falls off the bone, ladle it into jars and process them.
Fourth, if my electricity goes for a few hours out I don't really care. Well, I will care, because my icecream will melt- but I won't lose a freezer full of meat.
Fifth, portion control. Meat is expensive, and I find that if I carefully portion how much goes into each jar, and use one jar per meal, we use less meat per month overall and therefore spend less on groceries.
