In complex technical environments, it often doesn’t make sense to have an in-depth expert assigned to every system. You get a consultant in to set it all up and get the gears moving, but you can often get less experienced, or more versatile, people in to keep it running.

Also, the demand for skills has been silly for the past 20-odd years, so there’s less incentive stick around, other than money. Loyalty rarely pays off, unless you’re talking shares.