One tire has way more wear than the others — why?

Also make sure they're rotating your tires every 5,000-7,500 miles. If you went 35k without a rotation, the front tires carry more weight and do all the steering/braking, so they'll always wear faster than rears. A rotation every oil change keeps wear even.

Uneven wear on one tire is almost always alignment-related. Specifically, the toe setting on that wheel is off, causing it to drag slightly instead of rolling straight. This eats the tire fast. Could also be a seized caliper on that corner causing the tire to spin under braking. Before putting new tires on, get an alignment and have them check the caliper. Otherwise your new tire will wear the same way.