> Through the entirety of human history you'd keep working for the same employer for your entire life
Just looking at the Western world that breaks down during industrialization and falls apart if you go further back then that, journeymen (i.e. tradesmen who had completed their apprenticeship) would often literally travel from town to town for several years to work under different masters before submitting their work to a guild for evaluation and becoming masters themselves. I guess you could say serfs worked "for the same employer" because their feudal lords owned them as part of the territory but that seems like a stretch.
It's not so much that employees used to "keep working for the same employer for their entire lives", it's more that the people running and operating businesses used to be part of a local community and there used to be an understanding of a shared responsibility beyond private property claims.
This isn't something employees can change, either. Even employers aren't really able to change this because they too have to operate in the same economic system that contributes to this effect. It's probably more extreme in the US (and some places in the US more than others) but the economic system does not care for such sentimentalities and a business that does will put itself at an economic disadvantage, especially where the social fabric has already been sufficiently eroded to avoid bad optics (e.g. WalMart arguably failed in Germany because its attitude to employees felt extremely off-putting both to workers and consumers at the time but that resistance may have been eroded by the behavior of other companies since to the point where it would no longer make them stand out the same way if they tried to re-enter the market now - economic changes making this unfeasible notwithstanding).