If it's done in the US, you can bet it's because it's billable.
@MrsMorton
It's billable because it is cost effective. It's far cheaper to monitor bp than deal with the effects of a second stroke discovered five hours after it happened, or whenever the overworked nurse has the time to take bp readings or check on patients overnight.
Insurance companies turn down bills for monitoring and interventions that are not evidenced.
Scoff all you like at the US and its health 'system' - patient care is as much determined by money in the NHS as it is in the US.
The difference is that there is money available in the US to deliver medical care that is proven to work. In the UK there simply isn't the money, and there's a great deal of ex post facto justification getting thrown around for lask of basic medical equipment.
And it was in Ireland that my dad was monitored 24/7, 30+ years ago.