Nurses wear inside of wrist to simplify taking heart rate, or at least they used to back when you actually had to count it yourself. Divers wear inside of wrist to avoid having to do an awkward posture change and instead just look down.
When I was young, we had kind of a surrogate grandmother who was a retired nurse anesthetist. She told us stories of the old days counting the pulse of patients, holding an eye dropper full of chloroform to add to the gauze mask over the patient's face when the pulse got too fast.
If she had too many cases close to the end of her shift, she'd have to drive home buzzed on chloroform fumes.
