James writes:

I would have thought that 100/60 is pretty bloody low.

It is.

Is the Doctor getting kickbacks from the drug company?

He is just being extremely conservative. I suspect he just doesn't want to
take him off medication.

I get told my BP is pretty good when it is 115/70.

It is.

Genrerally I am 120/80 and the highest I know about
is 130/80. I did get a reall high reading after cutting myself badly,
152/95, but that does not really count!

Injury and disease can temporarily raise BP. So can dozens of other things.
Unfortunately, there aren't too many things that lower BP, besides medication,
so if you have a lot of things raising it, and you can't identify those things
and eliminate them, you end up on medication. Diet and exercise are very
important, although some people might prefer medication without diet and
exercise requirements rather than be required to diet and exercise in order to
avoid the meds.