Preferences are where service quality and route quality meet, and the meeting is usually mishandled in one direction or the other.
Why it matters
Ignore preferences and you lose customers for reasons that never reach a report. Honour every one as a rule and the route book becomes a collection of special cases, each defensible, together unworkable. The operations that get this right do something specific: they find out what the preference actually protects before deciding how hard to hold it.
“Mornings” usually means a school run or a shift. “Not Fridays” often means one particular Friday a year.
How you notice it slipping
Preference notes accumulate for years and nobody ever removes one. The share of accounts with special handling rises steadily. Technicians work around notes that the customer has long forgotten writing.
What to do
One question does most of the work at booking: what would go wrong if we came at a different time? A real constraint produces a concrete answer. A wish produces a pause, and that pause is the whole distinction.
Sort preferences into tiers: real constraints, meaningful wishes, and notes. Honour the first, design lanes around the second, and let the third be context rather than policy. Then revisit the list once a year — preferences expire, and nobody tells you when.