They are grown by cut-rate farmers....These trees are destined to fail.
Bullshit, my brother owned a wholesale nursery for almost 20yrs, the Aussie mega-drought killed it a few years ago. Plants sold in department stores and supermarkets are grown on contract, often the buyer supplies the patented seed/rootstock via a third party to the contract. At harvest time the buyer's insurance company sends out an assessor to make sure the crop is in good health. The plants leave the "farm" in excellent condition, from that point onwards they start to die unless they are properly taken care of in terms of light, temperature, and moisture. Warehouses, the insides of shipping containers, vans, etc, are normally dark, dry places, there's also a limit as to how long you can keep an outside plant displayed inside a supermarket, which (unlike the insurer) the store generally ignores until the leaves start falling off. I've found that supermarkets that sell poor quality plants also tend to sell poor quality fruit and veg, most likely for similar reasons.
Besides, buying from a local garden center is so much more of an enjoyable experience.
Agreed, but they get a lot of their stock from the same wholesalers, just like the local fruit and veg shop gets their stock from the same wholesale market the big supermarkets shop at.