Humans will make excellent domesticated animals to use as pets (amusing slaves), slaves(cheap labor), or food (I”m betting on food). Otherwise It sure looks like planets are rare and valuable enough – and trade costly and useless enough – that they are the ultimate ‘good’ in the community.
Economics in everything.
Marginal difference produces trading incompatibility, and cooperative in compatibility. Investment in a competitor is a catastrophe – which is the less on I take from Colonization. Habitable planets are scarce *in time*.