It's tempting to assume a single-member LLC doesn't really need an operating agreement since there's no one to disagree with — but the document serves a different, still important, purpose depending on whether there's one owner or several.
Why single-member LLCs still need one
Without an operating agreement, a single-member LLC relies entirely on state default rules, and courts scrutinizing whether the LLC should be treated as legally separate from its owner (a "piercing the corporate veil" analysis) often look for whether basic formalities, including an operating agreement, were followed.
Multi-member agreements carry far more provisions
With more than one owner, the agreement has to address voting rights, profit and loss allocation, capital contributions, transfer restrictions, and buyout terms — the entire category of issues that simply don't arise with a single owner.
Converting from single to multi-member later
Many LLCs start with one owner and add members later — bringing on a business partner or investor. When that happens, the original operating agreement typically needs a substantial rewrite, not just an amendment, to address the new ownership dynamics properly.
Matching the document to your actual structure
A generic template that doesn't distinguish between these two situations often either over-complicates a single-member LLC's paperwork or, more dangerously, under-addresses what a multi-member LLC actually needs in writing.