The advice to use a strong, unique password for every account is sound, and almost nobody follows it, for a completely understandable reason: no human being can remember dozens of long, random passwords. So people do the only thing they realistically can - they pick a few passwords they can remember and reuse them across many accounts, perhaps with small variations. The trouble is that this is precisely the pattern attackers rely on. When one of those sites suffers a breach and its passwords leak, the same password is then tried automatically against email, banking, shops and business systems, and every account that shared it falls at once. The passwords a person can hold in their head are, by that very fact, the ones weak and reused enough to be dangerous.
A password manager resolves the contradiction. It is a secure, encrypted store that remembers passwords so the person does not have to, which means every account can finally have its own long, random, unique password without anyone needing to memorise any of them. The user remembers a single strong master password that unlocks the manager; the manager remembers everything else, fills passwords in when needed, and generates new random ones on demand. The impossible task - dozens of unique strong passwords held in a human memory - is replaced by a manageable one: a single master password, well chosen and well protected.
The security gain is large and specific. Because each account now has a different password, a breach at one site no longer endangers the others; the leaked password unlocks nothing else, and the automatic reuse attack that does so much damage simply fails. The passwords the manager generates are far stronger than anything a person would invent and remember, and the manager will also flag when a password is weak or has been reused, turning a vague good intention into something actually done across every account. For a small business, where a single reused password on one careless account can expose systems that hold customer data or money, this is a foundational improvement rather than a marginal one.
Two cautions make it work rather than backfire. The master password becomes the key to everything, so it must be strong and not reused anywhere else, and it is exactly the account on which to add a second login step so that the master password alone is not enough. And the manager should be paired with sensible recovery, so that losing access to it does not lock the owner out of every account at once. With those in place, a password manager turns the universal, quietly dangerous habit of reused passwords into per-account uniqueness that costs the user almost no effort - one strong password to remember, and a tool that handles the rest. For the amount of risk it removes, adopting one is among the highest-value security steps a small business can take.