The spanning tree is going to involve bpdu's to avoild loop . so to have bpdu guard on if the interface detected a bpdu then it would become errdisabled. The best way to use that feature was with the spanning-tree portfast feature because spanning tree
portfast would be for end devices. Having bpdu gaurd would then ensure that should someone unplug an end device and plug in another switch onto the portfast interface having bpdu guard would errdisable that interface so the network doesn't go down from a loop.
