> Because if you don't, someone who does is going to invade for energy and resources. Therefore, refusing to expand is a slow form of suicide, unless you can be somehow certain there's no entity like that in the potentially accessible space.

I've heard that described as "where are the supernova defense systems?" Of course, I'm not aware of any explanations for why it's physically impossible to have a relatively small system sufficiently "hardened" to survive a supernova, or perhaps a way to defend oneself (including hiding) that doesn't require stasis.