What you say is true, but tables at the very least give you an idea of what you'll be looking at. To discard them in an absolute sense would be assinine. Granted every rifle is an entity all its own and will shoot differently, but the tables are of use, otherwise why would they exist?
I mostly did handgun shooting until recently but the information I got out of the ballistics, recoil and trajectory tables that I found for rifles was of excellent use. I have shot a variety of different chamberings from several manufacturers in rifles since looking at them and the tables have all been pretty spot on; the various Shoot! software(s) floating around have been very useful indeed. Have you bothered to compare your findings at the range/in the field with the info in the tables?