My dear Strange: Save this statement until you are 70, then re-read it. You won't like it one bit, because you will most likely still be a very capable driver. You will think you are in the prime of life, because people stay healthy longer nowadays than before. I am 70, quite physically fit, and still working 30+ hours a week at volunteer jobs to help those less fortunate than myself. Some of the people I give rides to are younger than me, and already physically ruined! My problem is my 93-year old father, who won't quit driving. He's never had an accident, but his reflexes are slowing and his health is weakening. Just 5 years ago I thought he was doing fine. Since then he's cut back how far he drives, won't drive at night, avoids freeways, and thinks that's enough adjustment, so he won't quit entirely. It won't be long until that's not enough, and I am worried but unable to stop him.
The issue isn't reaching a specific age, it's about retaining ability. Some people age 50 don't qualify and some age 80 are just fine. I could support testing every 2 years starting as early as age 60, or whenever a doctor reports you to the DMV at any age, to protect society. That's not discriminatory. I'll pass that test today at age 70, no problem, but I'll take it to protect you against someone else younger or older than 70 who would be taken off the road by mandator testing.