Just buy some weights, or go running... work out like a normal human being. The watch nonsense seems like some bizarre marketing scheme, at best.
If you're self-motivated in this general direction, then yes, you're basically right. However, there are lots of others who need some sort of motivation/encouragement, etc. Compare the cost of a Watch to the cost of a personal trainer, a gym membership, a set of weights, running shoes and sportswear... There is a fair number of people who need to make a financial commitment before they do something that's ultimately good for them. One need not purchase any of those things to get some exercise, yet it's a huge business anyway.
In a more low-cost vein, there are lots of friends who meet regularly for a walk around the neighborhood... We are social animals; even a disembodied buzz on the wrist and a scripted reminder text can be enough to provide the outside engagement needed to get us moving in the right direction.
A lot of people need a bit of reward to keep doing something, and while the endorphin rush from a bit of exercise should be enough, it shouldn't be a surprise that kids like getting little gold stars on their school work, and everyone likes getting a word of praise from a family member/friend/employer, etc. The Watch may be a little, disembodied bit of tech, but the virtual badges it hands out provide people with something to boast of... they help scratch our need for approval from those around us.
At one level this is nothing more than a task-specific calendar that's able to confirm that the appointment has been met. How many people get through life without an engagement calendar? Or will you tell us that our memories should be sharp enough to remember all we need to do?
The entire world is a bizarre marketing scheme. This particular one happens to get a fair number of people off their butts and doing something beneficial to their health. Considering the lifespan of a bit of personal electronics (2-3 years), the cost per day of a Watch beats that of a Starbuck's coffee by a wide margin and will hopefully do a fair bit more good. When you consider that the Watch has many more uses than the Activity app, throughout the day, and the beneficial(?) effects of a cup of coffee (or carbonated beverage) lasts less than an hour, the cost-per-day of this particular feature goes even lower.
So sure, if you're so self-motivated that you can do without reminders, and so self-assured that you need nobody else's approval, then skip the Watch, and feel justifiably superior to those who need a $400 crutch. Whatever makes you tick.
