Wessex and Mercia have had a busy decade. Both kingdoms militarized their borders, fought off invasion forces, and even took the offensive and marched into neighboring kingdoms. And even though the Chronicle is mysteriously tight lipped on all of these fights, it’s clear that way more than just construction work was going on at all of the burhs.
There were battles being waged. Battles that largely went unrecorded for some reason… but battles nonetheless. We know this because other sources from that time tell us that real blood, sweat, and tears were going into the acquisition and defense of these border shires.