I suppose the first question we must entertain is why build 0.0 settlements/colonies on temperate worlds?
Settlements and colonies are distinct from forts and outpost (traditional sense).
To my mind, the research outposts of Antarctica represent the extreme of specialist settlement were the most critical supplies have to be imported. The outposts specialist populations are small and generally self-policing. The ISS is another example of a specialist outpost where everything has to be imported to support the small, self-policing, specialist.
Settlements and colonies are intended to be independently survivable. When the imports stop coming (for whatever reason), the settlement/colony does not simply disappear. It may no longer get certain goods or be flush with a resource it can't directly use (its export), but it continues to exist sans support of some larger whole.
Is a colony more challenging from an infrastructure perspective than an outpost? Yes! But if you need more than 10,000 people to achieve your goals, then a colony might actually make it cheaper (per person).
In Eve, we setup Starbases (temporary outpost) and can establish Outpost (permanent settlements). Outpost are larger than Titans. Assuming a Titan has 150M m3 total volume (less than Avatar), 15% habitable volume, and there is 75-100 m3 per person; you get a population on a Titan of 200-300k. Back to outpost, they are big, say 500M m3 with 20% habitable volume, and 100 m3 pp; population on the order of 1M. Gallente Outpost a few more, Caldari a few less, etc...
As mentioned, living on the frontier were you can get shot is dangerous. These inhabitants also work for capsuleers and thus get paid lots when compared to a counterpart in high sec. Protein delicacies get boring after a while and there are "virgin" temperate worlds nearby.
The initial temperate settlements might tie directly into the economy of outpost by providing relatively fresh food for the station population. I-MGAB (as an example) is dozens of systems away from high security space with a mix of Sansha pirates and roaming crazed capsuleers who shoot anything that moves! Unless the capsuleers can find room to move the goods desired, they are going to arrive via a stealthy ship and in small quantities more likely than not.
So, while the initial infrastructure for a temperate colony or settlement will be expensive, it could pay off in terms of more secure and readily available access to "luxury" items for in-space colonies.
The District has approximately 4 million baseline Outpost dwellers and 4 temperate worlds (& 2 oceanic), populations uncounted at the moment.