Why arrangements drift without anybody deciding
Drift is rarely deliberate. The cleaner finds a faster sequence, an area gets skipped once during a busy week and then again, a periodic task slips by a month and nobody notices. Each step is small and reasonable in isolation. After six months the service delivered is measurably different from the one described in the proposal, and neither party set out to change it and nobody can point to the moment it began.
It is much easier to correct early. A conversation at six weeks about an area receiving less attention than intended is straightforward, because the arrangement is new and both parties expect adjustments. The same conversation at month eight is harder, since the pattern has become normal and raising it implies a criticism nobody wanted to make earlier and the provider can fairly say the point was never raised at the time.
