Consistency matters because search engines use agreement across sources as a confidence signal. When the same name, address, and phone number appear identically everywhere, that is corroboration. When they disagree, a system deciding whether to show you has to guess which version is right, and uncertainty is not neutral. This is one of the more direct ranking factors in local search, and it is entirely within your control.
The disagreements are usually trivial and that is what makes them easy to ignore. Suite 200 in one place and Ste. 200 in another. A phone number from before you switched providers. An old address from a previous location. Your name with and without the LLC. A category that was auto assigned and is close but not correct. None of these look like problems and collectively they weaken the signal.
Fix them in order of consequence. Your Google Business Profile first, because it is what most local results are built from. Then Apple Business Connect, which covers everyone asking Siri or using Apple Maps. Then the major aggregators, which feed dozens of smaller directories from a handful of upstream sources. Then anything specific to your industry, which often carries disproportionate weight in a narrow category. Write down the exact form of your name, address, and phone number first and use that string every time rather than typing it fresh.
Duplicates deserve separate attention. Two listings for the same business split your reviews and your authority between them, and one of them is usually wrong. Most platforms have a process for merging or reporting duplicates, and it is worth the twenty minutes. Then check again in six months, because data providers refresh and old information has a way of coming back.
Write down the exact form of your details and use it as the source, because the drift happens through retyping rather than through decisions. Name including or excluding the legal suffix, address abbreviated or spelled out, phone formatted consistently. A single line in a document, referred to each time rather than recalled, is what prevents the accumulation of small differences that weaken the whole set.