Leather dries out over time when left to sit and becomes brittle. It must be treated with some thing like a leather oil rub or "saddle butter". Fake leather is similar.
When you wear them regularly from new before they dry out, the sweat and oil from your skin goes a long ways towards keeping the leather pliable.
Artificial fabrics obviously don't have this problem, unless exposed to sunlight.
Mink oil is good to have but I've never found anything to top Bicks #4 conditioner. It took me years and several thousands of dollars of leather products to cave and buy a bottle and I'll never use anything else. If you're serious about leather care, I'd recommend it highly