Well they've got a couple things going for them— they're sealed so there's very little chance of cross-contamination in transit or storage, and since it's a ready-to-eat food item rather than a raw ingredient, at least the more reputable companies probably need a pretty solid HACCP plan (short for Hazard Analysis and Critical Control Points— a formal for safety risk analysis and their mitigation procedures), which means at least someone is paying attention. But that's not a guarantee of course, as we've seen from McDonald's current sliced onion debacle, or Boar's
Head's recent listeria recall that lead them to discontinue liver wurst and shut down their huge plant in Virginia. Either way, it's probably safer than store-cut stuff, but there are a lot of factors.
The big problems I've seen with greens all came from field contamination that couldn't be washed off, but that could also be because other types of contamination don't have a single source point and therefore don't trigger a recall/definable outbreak/news coverage.
And when it comes down to it, these are natural organisms that don't come from industrial food production, and will always be somewhat of a risk as long as we eat natural foods. Botulism spores naturally occur more frequently in parts of the western US in places that grow a lot of garlic and onions, which is why we need to refrigerate garlic oil and such— industrial food production is excellent at killing botulism and cases of poisoning come from improperly prepared home canned goods, because doing it 80% right kills everything else, and you could go 3 generations using that recipe before getting over contaminated with botulism, and then everyone at dinner that night dies. Eating industrial canned food exclusively could eliminate most risk of pathogens altogether, but then there's other risks like chemical leeching in many products, nutritional considerations, other contamination (normally a negligible risk, but would it be if you only ate industrial food?) and who really wants to do that, anyway.
But in the US, no for we sell is as risky as raw chicken. Not by a long shot. It's really bizarre that the FDA is so upright that they won't allow soft raw milk cheeses to be sold, but the USDA still, I believe, doesn't legally classify the deadly Salmonella Heidelberg to be an adulterant, as they do e. Coli OH157. Not sure if it's outdated, but when I was in culinary school some time ago, 1 in 4 chickens had enough Salmonella or campylobacter to make a healthy adult sick.
The most impactful things it seems to me home cooks can do to reduce their risks are a) don't to anything else while cutting raw meat, and immediately wash everything that touches it as soon as you're done, b) invest in an instant read thermometer if you cook meat that has a lot of surface area exposure to equipment (e.g. ground meat, sausage, cube steak), c) don't keep cut melons or bean sprouts for more than a few days, d) keep all uncooked meat in the bottom of your fridge below everything else.
There are other things that are risky that people don't realize— cooked room temperature rice, raw flour, room temperature brewed tea, etc etc etc— but they're less frequently problematic. It's a risk/reward just like anything else. A tea shop in Boston made a ton of people sick not refrigerating it's iced tea some years ago, but it didn't kill anyone, and lots of people have made sun tea without getting sick. People WAY overestimate the risk of eating raw eggs, but something like 1 in 10k eggs could do it.