Some drains have known, not-yet-repaired weaknesses: roots that regrow each year, grease-prone kitchen lines, silting stormwater runs. Preventative maintenance schedules jetting or cutting at intervals shorter than the problem's return time, with periodic CCTV to track any deterioration.
It is the rational middle path between emergency-only reaction and immediate full repair — and for strata and commercial sites, it is standard asset management.