Omaha Steaks says they use it (only) for ground beef because, "Unlike solid cuts of meat, the potential exists that surface bacteria may have been mixed within ground beef."
Wegmans has a cooking temperature page[4] that gives lower temperatures for irradiated ground beef than for regular ground beef.
So that's one way safe + rare is possible.
Another way is sous vide. It's a "low and slow" cooking technique, and germ-killing is a function of both time and temperature[5], so it can achieve safe + rare. It's definitely more trouble to cook your burgers for 1-2 hours, though.
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[1] https://ccr.ucdavis.edu/food-irradiation/are-irradiated-food...
[2] https://www.supermarketnews.com/archive/wegmans-offers-own-i...
[3] https://www.omahasteaks.com/servlet/OnlineShopping?Dsp=5707
[4] https://www.wegmans.com/final-cook-to-temperature-charts/
[1] https://www.cdc.gov/vibrio/vibrio-oysters.html
[2] https://www.cdc.gov/foodsafety/communication/salmonella-and-...
Cooking at home one is typically using a significantly smaller amount of ground beef from a smaller batch, so lower chances overall of some bacteria from one package of beef being distributed across a large number of burgers.
Additionally most bacteria that gets onto food prepared in reasonably clean environments doesn’t do much more than cause an upset stomach.
There’s liability at restaurants on the above for the reasons you mentioned, where those same liabilities don’t exist for steaks as highly. At home, all bets are off on liability from being undercooked.
Still though I wouldn’t eat rare burgers at home.
When I'm at my supermarket meat counter near closing time, they are washing everything -- equipment, countertops, walls, floors with hot soapy water, brushes, and a hose. Everything goes down the floor drain.
When I worked in restaurants, equipment was mostly cleaned with rags and a bucket.
I don't know what 'restaurant' you were at that used rags and buckets, but it certainly would have failed health and safety regulations.
Source, 15 years as a chef.
I generally get med-rare burgers from places that ground their own meats recently, so streak houses that ground the steak trimmings from yesterday that morning. Else I'll order medium and not risk it, but everyone's risk profile is different.