From where I've been sitting, big box retailers have been running on the zeal of expansionism for decades now.

No profit? Then by all means they can sit back and let Dollar General come in and capture the retail of a town.

In the past this has generally been bad news for an entrenched retailer and the first signs of fracturing. It's hard for me to care too much though what happens to these big chains.

I think you are mixing up cause and effect. It might be a bad sign for a retailer if it has unprofitable stores, but that doesn’t mean keeping them open is going to help.