Having been in CE, I might be able to shed some light on why they're renovating rather than building a new BX. It's about the funding regulations mandated by Congress.
I'm pretty sure AAFES and DECA have to follow standard government construction rules, as dicked up as they are. What you're seeing is actually all driven by Congress, not AFFES, not DECA, and not Big Blue.
There're two pots of money - MILOCON (Military Construction) and O&M (Ops and Maintenance). With O&M, base and Majcom spending authority is pretty high, into the $ millions, IIRC, the timelines for funding are much shorter, and the amount of discretion in how the budget is spent is much greater at base and Majcom level.
For MILCON, the funding limit at SECAF level used to be $300K back in the 90s, but is likely to be about $500K now. In either case, it's about enough to build a small garden shed and not much else. Any "new" construction costing more than that and the project has to go into the DOD's budget to Congress as an individual line item with full cost estimates, project justification, and environmental assessment. Typically it takes 3-5 years from concept to funding approval to go the MILCON route.
What that means is that CE gets pretty creative in how they classify work. I can't remember all the specific rules, but they're something like, if you can keep 51% of a structure, you can do nearly anything you like under the O&M rules because, the logic goes, you're merely maintaining an existing facility. So, you keep the shell and foundation of the BX, rip out and replace everything else. You could even put on a small addition to the building if you wanted but that addition would have to be costed out separately and can't cost more than $500K or it has to go into the Congressional budget and takes years.
There was the case of the Ramstein O'Club back in the late 80s where everything of the old club was demolished except one wall and from that was built an entirely new club under O&M rules, all as a way to circumvent the MILCON rules. That was taking the piss and some wrists got slapped over that one.
I'm not necessarily trying to defend my CE brethren, because CE can still be pretty screwed up, but if you work in CE for very long you become extremely adept at "working the grey zone" of the regulations and CE actually delivers quite a lot given the rules they have to bend every day.
I include this only so you can direct your fully justified anger at the right target - Congress.
Oh, yeah, and I hated AAFES as much as some of you. Self-absorbed thieving bastards, was my view, and hanging was too good for the lot of them. When they tried to have the squadron snack fridges shut down or run by themselves because they saw them as competition was when they really just went way over the line.