Why would scientists be genuinely interested in gain of function research?

There is a big strategic priority in the US and other countries around preparedness for biothreats. Particularly from parties that are not a part of any well regulated entity or groups that follow / adhere to international agreements. Biothreats often include taking clinical pathogens and modifying them to enhance a biological feature (e.g., resistance to certain treatments/drugs, ability to increase spread capability, increase virulence).

If you were charged with being the front line defense mechanism to deal with biothreats, you might want your scientists figuring how mechanisms that could weaponize something that has already shown virulence (e.g., Ebola) might be countered? Is there a vaccine that would work, are there counterpathogens that could counteract the virulent strains, etc? Its difficult to have preparedness and to have fast response capability if your scientists haven't studied those mechanisms. Because its very hard to figure it out just by capturing those biothreats after the fact. So you have to have a sense of what things are possible, which things are harder and easier to execute, and how long lasting and impactful particular designs might be.

Its dangerous because of course these things can become weapons and dangerous. But if you consider yourself the "good guy", which of course everyone does in their own mind, it seems irresponsible not to work on them in well controlled contexts (e.g., BSL Level 4 labs).