It's not that blood pressure reading aren't useful, it's just that this is marketed as a "fitness watch" and not a general blood pressure tool.
Now I have seen some suggestion that blood pressure could be used to predict how hard you can train on a given day in the same way that heart rate variability can be used. That's really interesting.
A blood pressure reading on it's own though, without any clever interpretation, seems much less compelling in a sports product.
If this is just marketing to make blood pressure monitors more "sexy" I guess that's fine too just less interesting if you have an actual sports goal in mind.
Hypertension or high blood pressure can affect all age groups (I was diagnosed at 17) but more prevalent from middle-age on wards.
Use case is that having a wrist watch measure your BP, can make it super-easy to monitor. Right now I have a digital one at home but hardly any motivation to use it. BP is well managed with a bit of exercise and medicine so I am hoping the watch will be useful (not withstanding all the questions about accuracy).
I'd say like anything health related you want to see changes over time. If something suddenly changes for the worse you know something new is going on.
That's why I like have access to consistent health care in my country. Something like an overall rise in blood pressure isn't necessarily something a person will notice. High blood pressure is described as the "silent killer".
The first image you see on the page that has people in it (rather than their hands) is indicative of the target market: middle-aged men with tan coats who feel happy when walking on rocky beaches with a happy middle-aged woman hugging their arm.