Really this is what people think? For me it’s always been the opposite, use as little as possible to leave a lot head room, as much as possible. That’s like saying a gas guzzling car is more efficient than one that uses much less fuel.
Following your example of cars, having a large gas-guzzling full-size truck when you drive by yourself 5 miles to the supermarket once a week would indicate that the vehicle is being used at a low percentage of its capacity. If it were loaded up hauling heavy equipment and materials, to and from jobsites for example, then it would be near 100% capacity.
For the weekly grocery run, it is wasteful to have this truck since it is used at low capacity. One would be better served with a much smaller vehicle, even perhaps one that is human-powered (such as a bicycle).
"Ideally, the resource gets used at 100% of its capacity: we have enough capacity to serve our needs without generating queues, but not so much that we’re wasting money on idle resources."
The large (expensive) truck only used on the grocery run would be wasting money on idle resources, since it is capable of doing much more work but is rarely used.
Taxis are on the other end of the spectrum.
That's what they mean when they say "markets are efficient". Side effects of this ideology are stressed out people and destroyed planet.
Or, if given many widget machines and noting that only one or a few are "necessary" (in theory), they retool or sell off the excess (probably not all at once, it's a little-by-little thing). Which leaves them unable to handle excess production when it's needed, or to handle when one of the machines is down for maintenance or repairs (which it will need more often, it's running at 100% so will breakdown faster and there's no time to turn it off for regular maintenance).
No idea why people actually think 100% utilization of any resource would be a good idea... I guess it helps if your 100% are including pointless meetings as part of "productive" time.
Seems like people are mixing up utilization and efficiency.
High utilization can definitely lead to reduced efficiency.
To use your car analogy, it's like buying a car when you need transportation 1 day a year. That's inefficient because that resource is unused 99% of the time. Far smarter to get an Uber for one that day.