Specifically those involved in genetics, breeding practices, and mobility/SD work. @impish-iggies, @doberbutts, (or if you can boost this to those who could answer my question.)

Why would a breeder choose to not test for some joint clearances (such as shoulder and patella)? Is it a lack of reliable tests issue, money and costs, age?

Since my sis and I are looking at Greater Swiss Mountain Dogs as a mobility/service dog we are concerned about the longevity of joints after years of support work. Apparently in GSMDs clearing shoulders and patellas isn’t a standard practice. Why would this be?

Also, how important would those joints be in our decision for a breeder? (ie, the nearest breeder we like has cleared 2 out of 3 of their studs but none of their bitches, why?)