Every tenant move-out leaves cable behind. Nobody pays to remove what they are walking away from, and the building rarely forces the issue. Twenty years of churn later, risers and plenums carry more dead cable than live, and that dead cable is not neutral clutter.
Three problems in every bundle
It is a code violation. The National Electrical Code (Article 800 and related sections) requires the removal of accessible abandoned communications cable, defined roughly as cable not terminated at equipment and not tagged for future use. Fire marshals cite it, insurers note it, and after an incident it becomes exhibit material.
It is fuel. Cable jackets burn and older jacket compounds produce dense toxic smoke. Fire load in vertical shafts and plenums is exactly where you want less combustible mass, not more. This is why the code provision exists.
It is capacity theft. Sleeves and conduits are finite. Buildings routinely core-drill new penetrations, at thousands of dollars each, with structural and firestopping implications, while existing pathways sit full of cable that serves no one.
Why it never gets fixed
Because removal requires knowing what is dead, and that requires documentation nobody has. Pulling the wrong "dead" cable takes down a live tenant, so untraceable cable is treated as immortal. The abandoned mass grows by default.
The way out
Reconciliation: a field audit that traces and attributes every cable, an ownership determination for the unclaimed remainder, a tag-or-remove decision per NEC, and, critically, a move-out standard that stops the accumulation, requiring departing tenants to remove or formally abandon-in-place their cabling with documentation. Buildings under governance stop accumulating the problem; buildings without it re-fill their risers every leasing cycle.