OTOH, with your vehicles, you then need a technological infrastructure to maintain them, to re-energize them, to reproduce them, to create parts - you could go all the way back to needing to mine the minerals and refine them if you can't trade for the parts with visiting ships - ships you can't necessarily count on to arrive carrying what you need when you need it. These are backwater worlds, remember - they're most likely not on regular carrier routes. These people have to be self-reliant, and they need transportation that is easily replaced if it can't be repaired - a horse fits that bill a lot better than a hovercraft. On the outer worlds, it's the tech that's a luxury; what we see as "the Old West" is about the minimum level of technology to which any modern human being would need to descend when homesteading a suitably-terraformed planet, and they can augment their lifestyle with higher tech, but they'd be foolish to think they could rely upon it as their primary means of living.