Not just handwashing...

There's a theory popular with jaded biologists that neckties alone may have killed more people than some minor genocides.

And the failure to perfect the practice of hand-washing is somewhat easy to understand: it's tedious, especially when done dozens of times per day. Some people suffer skin irritation. The cause of any infection can almost never be traced, making it hard to learn and/or punish the guilty.

Banning neckties is a rather binary policy decision, and compliance would be extremely easy to monitor. One would think people with advanced academic degrees would see the upside, and don't need to signal status with superfluous items of clothing in addition to that doctorate.