An office building owner receives escalating complaints from his tenants about how long they have to wait for the elevators.

The owner calls a civil engineer to ask what he could do.  The engineer suggests the building can structurally support another two elevators.  It will cost about 5 million dollars and the building will need to be closed for 6 months.

Shocked he calls in a computer science engineer instead.  The CS guy mentions he’s been working on AI lately and can write a learning algorithm that can adapt to the schedules of the tenants and can position the elevators more effectively for shorter wait times.  It would take about 6 months about cost about $300,000.

The owner finally calls a systems engineer.  The systems engineer quickly suggests putting a TV in every elevator lobby and no one will complain again.  The tenants will be distracted even if watching a terrible show and not perceive the slowness of the elevators as much.  The simplest and cheapest solution avoided complaints.

The tie in with web front-end performance is even if you do not actually improve the full load time at all, if you can improve the perception of the users that things are happening or they have something to view and read in the meantime it demonstrably increases the amount of people that will stay on your site rather than click away.