Philosophy is not considered science because it lacks:

reason

logic

experimentation

writing

I think ans is experimentation because logic and writing is important in philosophy

Philosophy is not a science because it lacks solid, mathematically confirmable results.

What is the energy of a baseball hitting a wall with a speed of X and a weight of Y and a medium of Z? Science (physics). Results in a solid, repeatable number.

What should the energy of a baseball of a wall be? More than that of a cell phone? Why? No answer. Philosophy is, at best, talmudic debate.