The failure in small businesses is almost never a bad decision. It is the absence of a record. Nobody wrote down the exact colour, so the next graphic uses one sampled from a compressed image and lands two shades off. Nobody recorded the typeface, so a document uses whatever was available. The logo exists in six versions across three folders and the one used is whichever was found first. Each individual instance is defensible and the cumulative effect is a business that looks improvised.
Consistency also carries a practical weight beyond appearance. Your name, address, and phone number appearing identically across directories is a signal search engines use to build confidence that you are one real business, and disagreement between sources weakens it. That is the same problem in a different domain, and it has a measurable consequence in whether you appear in local results.
Fix it with a document rather than with discipline. One page recording the exact colour values for screen and print, the typefaces and where to obtain them, which logo version is used in which situation, and the standard description of the business in one sentence and one paragraph. That document is the entire solution, and it takes twenty minutes to write while everything is still fresh.
Then use it as the source rather than working from memory or from an existing file. Sampling a colour from a previous graphic propagates whatever error was in that graphic, which is how brands drift a shade at a time over a year. Every new piece starts from the recorded values.
Where consistency should not be rigid is tone across contexts. The same business writing a legal notice, a social post, and an invoice reminder will and should sound different in register while remaining recognisably the same voice. Consistency means the underlying character does not change, not that every sentence is interchangeable, and treating it as the latter produces writing that reads as manufactured.
Audit it once a year by collecting everything a customer might encounter and laying it side by side. Your website, your business profile, an invoice, a printed card, your email signature, your vehicle if you have one, and your social profiles. Seen together rather than individually, the inconsistencies are obvious and usually take an afternoon to correct. Seen one at a time, which is how you normally encounter them, each looks fine and the drift continues.