The buyer arrives sceptical, and usually burned. Small and mid-sized business owners searching for an agency have frequently paid one before and received a monthly report they could not read. So the search is short and the evaluation is long: they type something like an agency search for their city, open several tabs, and start hunting for tells. Vague deliverables, no named team, a stock-photo team page, a blog that stopped a year ago. Every one of those is a reason to close the tab, and none of them are about ranking.
Competition on these terms is the most aggressive of any vertical, for the obvious reason that everyone bidding is a practitioner. Directory listicles occupy much of the first page, other agencies bid on your brand name, and cost-per-click on agency terms sits among the highest in local services. That changes the economics: an agency's own campaign generally cannot win by outspending the field, so it wins on the strength of what happens after the click and on terms too specific for the listicles to bother with.
There is also a second buyer nobody optimises for: other agencies and in-house teams looking for a partner to handle a discipline they do not staff. That traffic searches partnership language rather than service language, converts faster than a cold owner, and often becomes recurring revenue. Most agency sites have no page for it at all, so the inquiries arrive by email or not at all.