Most of what you name—physics and mathematics and astronomy—were once considered parts of philosophy, and philosophers were the people who did them. That's no small part of why PhD stands for "Doctor of Philosophy."
What you're complaining about is actually the specialization of certain branches of philosophy into their own separate disciplines. A physicist today no longer thinks of himself as a philosopher, except perhaps if he glances at the diploma on his wall. That does not mean that he is not a philosopher in the same sense in which the ancient Greeks used the word, namely as one who loves wisdom, and in which Plato would have understood the term as he pursued not only moral philosophy but also mathematics: Plato would almost certainly see a physicist as a philosopher. Anyone pursuing theoretical knowledge with no direct utility to daily life (unlike, say, pottery or baking) was a philosopher.
After all the specialization that has happened in academia, the people who still call themselves philosophers constitute a husk of a discipline. They mainly contemplate logic (but not computer programming), epistemology (but not neuroscience or psychology), and morality. Seeing them as the only philosophers, rather than as the one group of philosophers who didn't bother to come up with a new name for themselves, is a mistake.
What you're complaining about is actually the specialization of certain branches of philosophy into their own separate disciplines. A physicist today no longer thinks of himself as a philosopher, except perhaps if he glances at the diploma on his wall. That does not mean that he is not a philosopher in the same sense in which the ancient Greeks used the word, namely as one who loves wisdom, and in which Plato would have understood the term as he pursued not only moral philosophy but also mathematics: Plato would almost certainly see a physicist as a philosopher. Anyone pursuing theoretical knowledge with no direct utility to daily life (unlike, say, pottery or baking) was a philosopher.
After all the specialization that has happened in academia, the people who still call themselves philosophers constitute a husk of a discipline. They mainly contemplate logic (but not computer programming), epistemology (but not neuroscience or psychology), and morality. Seeing them as the only philosophers, rather than as the one group of philosophers who didn't bother to come up with a new name for themselves, is a mistake.