Bloodwork - markers - question

I have asked repeadly why tumor markers are not done rountinely and was told the same answer. That they are not reliable and the insurances will not pay after one person reaches the survival time of 5 years with no recurrence. I had a friend that went through this and she has to pay out of pocket (she is a nurse). None of them work on me and for a long time we thought they did then we figure it out when I had recurrence they were still normal and have never moved since surgery. But, then none of these tests are 100% so they do the best they can with what they have to work with. Hugs, Sandy