Also potentially useful if you're involved in any way in policy formation. (And yes, even when there are political constraints).

In practice, I find the most useful aspects of having a working knowledge of lots of different ethical systems is that it makes it easier to:

(a) quickly drill down to the core of many disagreements. Even if they're not resolvable, being able to find them quickly often saves a lot of pointless going around in circles. (There are network externalities involved here as well. Knowing this stuff is more valuable when other people know it too.)

(b) quickly notice (or suspect) when apparently sensible goal sets are incompatible (though this is perhaps more to do with knowing various impossibility theorems than knowing different ethical systems).