From this site:
and:
Thanks folks, for the correction on the cause of the crash.
B-52’s become very cost-effective when you consider the rest of the bomber fleet - we only have a few squadrons worth of B-1B’s, and the B-2 (which BTW did fly combat missions in the Balkans) has only been approved for limited production run - maybe a couple of dozen.
Meanwhile, we’ve got hundreds of B-52’s which are a proven workhorse with enough spare parts/enignes/airframes in desert storage to keep the current fleet flying for the forseeable future. Hell, if they had to, they could probably build a whole new fleet of “FrankenBUFFs” from the decomissioned airframes in the AMARC facility at Davis-Monthan AFB…
As for Gulf War use, the bomb racks for delivery of conventional bombs from a B-1B were still considered “experimental” and hadn’t been fitted to the whole fleet. This isn’t the only reason they weren’t used, but it is one of them.
I happen to be working on a B-52 program right now. A few tidbits…
As many others have already noted, the primary reasons for the B-52’s continuing success are low cost and simplicity. The former is extremely important for obvious reasons. (Believe me, every penny is being pinched right now in the USAF.) The latter is also important; compared to new bombers, the B-52 is a piece of cake to maintain and troubleshoot.
Another thing: there are only about 75 active B-52’s. There are another 10 that are activated/deactivated as needed to keep the number of active B-52’s at 75. (Note to gov snoopers: this info is not classified, and readily available). I also believe NASA has one, though I’m not sure what they use it for.
The lifecycle of the B-52 is expected to last until 2040. This means that the pilots who will be flying the B-52 during this time aren’t even born yet. Wow.
NASA uses the B-52 to launch test aircraft, such as the X-15 and so forth. They still use it for that purpose. (I’ve touched that B-52! 
)
Smithsonian Air and Space magazine just ran a feature aricle on NASA’s B-52, one of the earliest ones built. They are stil l using it for air dropped vehicles. The other NASA buff that carried X-15s is retired to the Pima Air and Space museum in Tucson, Arizona.