That's understandable. If you could join a larger tribe and keep a homestead, would you do so?
If there was a closer large tribe, would you use their facilities?
With the coming building use updates and allowing players a homestead and a tribe, I am hoping there is enough incentive for several tribal centers to exist throughout the map so that all players have relatively easy access to them.
Point taken regarding what fits in a 'sandbox game'. Xsyon was conceived long before I had ever heard the term 'sandbox game'. It was partly inspired by Ultima Online, which did have NPC vendors.
Regular NPC vendors were never part of Xsyon's design, but 'trade with tribes beyond the mist' as a way of introducing some items into the game was. It was intended to be a bit different, with totems on the edge of mist, not in tribes, but the concept remains the same.