Ethics is that incentive.

Would you be fine getting a good salary for legally building bombs that are sold legally, knowing that they are purposely killing many innocent children? If the answer is "no", then it means that there is an incentive. You "just" need to find your line.

And I strongly believe that sometimes, the only way is to agree together on a line (through regulations), because individually we may not be strong enough. For instance I think that sending people to the ISS/Moon/Mars is an artistic performance that the world does not need. On the contrary, we invest a ton of public money into doing that, which then unlocks private companies (like SpaceX) to commoditize space, which in turn is bad for the environment. So I would vote against spending public money on this. But now if you offered me to become an astronaut in a space program, I would most definitely go. I find it interesting: I would vote against it, but given the opportunity I would do it :-).