There are a lot of occupations where you don't have your own computer, and share one with many other people.

For many jobs, the value is not in the person, but in the position, so the position has a single computer for a function that multiple people fill. Especially if you work for a company that operates 24/7.

For example, each person person operating a control computer at a recycling station does not have his own computer. There is a computer for each position, and who mans that position will change from day to day.

Freight dispatchers, retail sales, customer service, airline operations, and many broadcast positions are in the same boat.

Imagine how big an airline ticketing counter would have to be if "In this day and age, you should not login to anything from someone else's PC" was reality.

If you're mixing work resources and personal email (or vice-versa), you have a problem. You should never hand off control of your intimate personal life to the security (or lack thereof) of your employer. And vice versa; your employer should not trust putting their intellectual property on questionably secured personal computing devices.

I've never worked for an airline, so I can't say what happens in that specific scenario.

However, when I worked for a chemical company, printing out the hazardous materials labels for sample drums that were shipped all over the country, the computer had a single common login for all users.

I don't see how that is a nightmare.