It's a frontier colony world, our town happens to be an old mine, but there's other settlements, they're just scattered.  We can get up to 99.9% the speed of light, but there's no warp or hyperdrive yet, so we still can't break that limit.  Earth is some ten lightyears away from it's closest neighbor, so pretty much anything that goes out to colonize space is going out there to stay.  There are worlds closer to Sol than Actaeon, and more densely populated.  Though it's been about sixty years or so since Actaeon was first colonized, it's still very much in its infancy as a populated world(Though, I am considering if we want there to be a primitive culture of native sentients). Some groups did come here for business, like AMI, but just like any frontier a lot of people come out just to find a place of their own.  Some even come specifically to get away from bigger government influence on more populated worlds.  The people of McDonough's Rest are among this second group.  

I don't think mecha(I've kept calling them titans, but I want a different name for them) need to have a specific origin.  It's enough to assume that they are the evolution of war machines such as tanks.  It could be said that they are particularly useful out in the frontier, where there's less infrastructure, and a weapons platform that can walk across any terrain, and even climb etc is invaluable.  

A form of AI was necessary to keep the mech's movements stable, and auto pilot was developed so that they could fight with or without a pilot(though they have always shown to be more effect with with a pilot).  They were developed to be smarter, to obey verbal commands and relay tactical information to their pilot.  These constant advancements, and a built in ability to learn created a sort of emergent intelligence.  A new titan is smart, but bland.  The older they get, the more their personality develops, and is shaped by their experiences with humans.  Some pilots form close bonds to their titans, anthropomorphizing them as humans often do.  By treating them as almost people, the pilots feed into the emergence of their personalities, and almost help to create them.  

Some pilots, however, don't care for this messy personality business, and will periodically factory reset their mecha's AI to maintain the professional, tactical machine that was originally built.  It has been argued that this creates a less effective AI, but there are no conclusive statistics on that.