Because the thing about the ear bones is circular reasoning. Here's why: all present mammals have 3 ear-bones therefore all mamammals known and unknown must have 3 ear bones. Mammals are defined as having mammary glands and there is absolutely no necessary connection between the ear bones and mammary glands. A more adequate connection might be made between live birth and mammary glands (and before the platypus was found such a connection was made - in fact in an article I posted earlier on this thread such a statement was made) but the platypus erased that from the list of "proofs" of being mammals. Now if you really believe in evolution then you must admit that at one time or another the ear-bones and the mammary glands were not necessarily to be found in each and every species. And that is why I say that paleontology is nonsense.
You might want to also point out that ONLY MAMMALS HAVE THREE EAR BONES. Ear bones are not present in any other group of critters -- reptiles do not have them, fish do not have them, birds do not have them and amphibians do not have them. As such, three ear bones are a very good indication that the deceased was a mammal and not a bird, reptile, fish or amphibian. Unfortunately, you seem hung up on mammary glands; do you have a boobie fixation?