1. Thinner tires are easier to puncture, as it is easier for a nail or road debris to get through the tread.2. Thinner tires are not going to provide good traction, braking, steering, particularly in wet or inclement weather. This is particularly true if you are using all-season radials in snow country.3. As tires wear, they can tend to "feather" as the blocks of tread wear on one edge (e.g., leading edge) and not another. This can cause the tires to get noisy over time, even if you rotate them often.4. As tires age, the tread gets harder and harder, which makes the remaining tread last an astonishingly long time, but at the same time, providing even less traction, braking, and steering abilities.5. Tires can dry-rot after about five years or so, and crack and even blow out.
6. Older tires can develop "flat spots" and lose their flexibility, resulting in shimmying, particularly when braking.
The "good old days" really sucked, and the next time someone says, "they don't make cars like they used to," reply, "Thank God for that!" The "Good Old Days" were not that good - or great.