The practical use of philosophy of ethics:

To provide a new reference frame for the negotiation of basic values in a society where "because God wants it" or "because it is unnatural" or "because we have always done it this way" is not convincing to many people.

The practical use of philosophy of science:

Most scientists don't want to waste too much of their precious research time on philosophical issues which leads to many scientists practicing a different point of view than they preach. Having philosophers exploring the discrepancies can lead to scientists who are actually aware of what they do which will improve their science overall.

It is similar for other branches for philosophy. And just as in other domains, the practical use does not turn up by focussing on the practical use, but by focussing on what is interesting.