While it is true that male pattern baldness develops to some degree in almost 100% of men and is inexorable - it continues in EVERYBODY until death, the RATES of progression are highly variable from person to person. "Non-balding" people also have male pattern baldness in a way, but their rate of progression is almost negligible. Think of it in limits fashion - the rate of progressio n of male pattern baldness of a non-balding man tends to 0+, but is NEVER equal to 0. The people who maintain full hair even at 70 or 80 are lucky enough to have such a low rate of progression. EVERY SINGLE MAN in this world starts to bald after puberty - but some lose it SO slowly that we never see them lose any noticeable amount of hair , other than the usual NW2 recession (that patch of hair above the temples is really sensitive to DHT, much more so than the other hair.)
Add to this the factors of age, DHT levels in the follicle, and susceptibility to DHT (which is also not a constant throughout an individual man's life) and it is evident that the rate of progression is variable even in the same individual. All hair follicles of all people will miniaturize if they possess sufficient DHT AND susceptibility to it. For non-balding men, either their follicles don't produce enough DHT, or (more commonly) the follicles don't have sufficient androgen receptors for significant male pattern baldness to develop.
In short, most people will NOT reach NW7. Remember that NW6 is quite different from NW7. NW7 is a severe, advanced form of male pattern baldness which always includes significant temporal recession (this is the TEMPLE hairline, not the
FRONT hairline above the temples, which is what we normally call "temples"), significant thinning on the sides, and loss of hair on the back of the neck. I've seen two guys who had lost all (and I mean ALL, unless you want to count 1 hair for every 5cm2 or so) the hair on the sides and back of their head as well. That is NW7+++, the worst possible form of male pattern baldness.
Cheers,
Arjun