Two things:

1. If you rode in the Appalachia, you'd be familiar with the numerous 18-22% grades we encounter around here, each being a few hundred feet long on average. On a bike with a pronounced race geometry, the chainstay would be 408-412 mm, which would drive me to slide way forward on the saddle during such climb if I want to keep my front wheel planted solid on the road, provided I wish to remain seated. This challenges my bottom's comfort, which I rank pretty high during distance rides (brevets).
Luckily, 2 years ago I retired my last bike with a short (408) chainstay, and now only ride bikes with 435mm long chainstays. The benefit is that no sliding forward is necessary on the steep uphills, which enables me to keep my sitting hardware precisely over the saddle area where I feel most comfortable.

2. Rear tire wears at a slower rate due to the reduced weight it bears with the longer chainstay. To you this may seem marginal as the wear rate differential is only of a few percentage points, but it matters to me given my average annual mileage and the unpleasant cost of the (Compass) tires I favor.