There are many reasons someone looses their natural teeth.  In the past it was common to extract a tooth instead of going through all the office visits and expense to save it with fillings and crowning, even a root canal.  Finances play a huge part in tooth restoration as it still does today, some people will have work done and pay for it while others will not.
Heredity plays a major role also, some people are predisposed to tooth loss, but with advancing technology and proper continuous patient care, more and more people of all ages are keeping their natural teeth longer and even permanently.
Many people that have lost their natural teeth have done so by neglecting to having them checked out or attended to when something has gone wrong, so instead of possibly saving a tooth, it “had” to be extracted.
So, even though your parents have lost their natural teeth, with continued proper care and attention to when you feel something needs attending to, the chances of you keeping your natural teeth to ripe old age is a good bet.
Take care,