In pre-civilisational societies (cattle-keepers, hunter-gatherers, caste-driven), tribal networks are the major ways through which access to livelihood and security are guaranteed.
After a successful hunt, you need to feed the entire clan, and not doing so is highly abominable. As the mantra goes, “yours is ours”. One’s socio-economic security and identity is built on these mutual gestures towards kindred.
In these primitive modes, these communities tend to be internally closed: they marry only their own, and have a special rudimentary attachment to place. When they settle in areas predominantly settled by other ethnics, they never integrate but constantly hanker to go back. Luweero residents reject candidate Tumukunde’s apology
With a hunter ethic (chase, trap, kill, and go), they actually behave like hunters bordering on thieves. To different degrees, almost all Ugandan ethnic communities with special exception of Buganda continue to build around this tribalist-primordial-hunting ethic.
But once societies are touched by modernity, individuals learn to live on the strength of their ideas and labour. Once their social and economic security is built on their intellectual/labour prowess, they can settle or marry anywhere. Etcetera.
This question of lack of a civilisational sophistication to Uganda’s past and present leadership explains the tribalism problem of the country.