[stcredzero]

Everything about living on Mars is hostile to life. Doing anything there like mining and manufacturing will be orders of magnitude more difficult and for what?

Wasn't there a fair bit of difficulty involved in building fleets of sailing ships and exploring the Earth? As it so happens, the reward for doing so was to become dominant in the new global geopolitical context. There's an incentive to keep up in the new expansion of context to keep from being left behind and engulfed in a larger context. The potential total population of the solar system, even based on just on foreseeable technologies, asteroid resources, and solar power could easily be in the hundreds of billions. Fusion power increases that potential by orders of magnitude.

It seems silly to be trying to rush to a place that wants to kill you when we have a great place here already that we could just stop messing up.

These aren't mutually exclusive things. And make no mistake: Many things involving ocean travel prior to the industrial revolution literally involved rushing to places that want to kill you, via another place that wants to kill you. Isn't rushing to a place that wants to kill you another kind of "doing things that don't scale (at first)?" If it means eventual geopolitical dominance in a future larger context, there will be wealthy nations willing to foot the bill.

[greedo]

It's been claimed that the high demand for timber is partially responsible for much of the deforestation of the British Isles. In fact, the demand was so high that the Colonies also provided a significant quantity.

http://www.wou.edu/history/files/2015/08/Melby-Patrick.pdf

[stcredzero]

The performance of the large American frigates may be partially attributable to the characteristics of American timber.

https://www.quora.com/Why-did-USS-Constitution-bounce-cannon...

In Roman times, the British Isles were also a significant source of lead.

https://en.wikipedia.org/wiki/Mining_in_Roman_Britain