Because a Google Business Profile competes from where its address sits, not from where the work actually goes. If the service area was never drawn, or was drawn as a radius rather than named towns, the profile is effectively a local business in one postal code. Proximity is a real ranking factor and distance genuinely works against you, so the next town is not simply a weaker version of your own - it is a separate contest, with different competitors, that has to be entered deliberately. Naming the towns is the first step; having something on your website that is genuinely about that town is what makes the claim hold.
Name the towns, do not draw a circle
Where the interface allows named towns, name them. A radius is a guess that usually does not match where the vans go, and it includes places you do not serve while missing places you do. Ten accurate towns is a stronger and more honest claim than a twenty-five kilometre circle, and it is also checkable, which matters more than it sounds.
A named area is a claim, not a ranking
Adding a town to the service area makes you eligible there. It does not put you in the pack. The businesses already ranking in that town have proximity, reviews from people in that town and usually a page that mentions it. Eligibility is the entry fee, and the rest is the work.
One page per town, and it has to be a real page
The temptation is to take one page and swap the town name into it twenty times. Google names that pattern specifically and it does not work. A page that earns a position says something true about that market that is not true of the one next door - who the competitors are, what the demand actually looks like, why the work differs. If a town cannot carry a few genuinely distinct paragraphs, it does not need a page, it needs a mention.
Expand one town at a time, and only where it is winnable
The right order is to hold the home town first, then take the next most winnable market rather than the biggest one. A competitive city with four established players and a decade of reviews is a long campaign; a town of eight thousand with three weak profiles is a fast one. Work out which is which before spending anything, and be prepared to be told your target market is not worth entering yet.
The follow-ups.
How many towns can one business realistically rank in? +
Will adding service areas hurt my ranking at home? +
Does a second physical location work better? +
Want me to check your own listing?
Nine minutes. I will run the search your customer runs, read you what I find, and tell you which setting is costing you the most. If it is already right, I will say so and we are done.