My mother OBM always tasted the meat mixture for hamburgers, meatballs and meat loaf and let us kids do so. She also was known to serve steak tartare as an appetizer on melba toast.
I still eat uncooked chopped meat.
That said, we do NOT buy ground meat from the butcher, or kosher supermarket. We grind or chop all our meat at home in our kitchen. Different blends of cuts are used for different dishes, as well as different consistencies.
Our favorite mix of cuts for hamburgers is ground neck and skirt with about a 15% fat content, less fat dries out to quickly on the grill.
For meatloaf and meatballs we use a coarser grind of shoulder steak about 7-9% fat. More fat yields a slimy feel in the mouth when eating these items.
Steak tartare is made with asst. cuts of chuck that are hand chopped in a wooden bowl with a hochmesser. It must have chew and bite to it. It is not a pate.
And as a reply to the OP, we never use ketchup in our mixes