Precision.
We demand precision in devices we buy, contracts we sign, rules of games we play.
Yet some people resist rules of grammar. Those rules help us to be precise — to write exactly what we mean, so that no one can misunderstand us.
The price of imprecision and misunderstanding can be very high, in either personal or business transactions.
Think about virtues in writing, among them a smooth flow that helps make meaning clear.
Consider this interruption of smooth flow: Peggy loved riding her bike, climbing trees and dolls.
That's a classic example of non-parallel construction. Peggy's first two loves are expressed with verbs ending in "ing." Parallel construction requires her third love to be expressed as "playing with dolls."
The lack of an "ing" verb produces a hiccup: an interruption of smooth flow.