It is not worthless. After getting a series of higher test results my doctor suggested a 24h test snd only then diagnosed mild hypertension.

Baseline blood measurements can also be invaluable. When getting sick you don‘t want to go down rabbit holes.

The US has a comparatively high hurdle to access to doctors. When doctors see patients they need to assume it is bad (liability another factor) driving costs up. Also people are not used to reach out to doctors letting them hesitate when they should not - regular contact can help here.

Every year major bloodwork and investigations may not be worth it but seeing your doctor regularly, being able to communicate effectively, doctor having a baseline of you as a person and some bloodwork too makes other countries a lot more efficient in providing health care.