The structure is deliberately shallow: no page is more than two clicks from the home page. Services and service areas are grouped under hubs so that internal links concentrate on the pages that can rank, rather than scattering across a flat list.
Why the hubs matter
Without hubs, the seven service pages and the ten city pages would each hang directly off the home page. Every one of them would compete for the same internal links, and none would gather enough to rank well.
With hubs, the progress is: the home page links to two hubs, and each hub links to every page beneath it. The hub becomes the page that concentrates authority, and the pages beneath it inherit some of it. It also gives a visitor on any page a sensible way to see everything else in the same group, without returning to the home page.
Two pages are deliberately excluded from search
Thank You is excluded because it confirms an enquiry rather than attracting one, and because a page that only makes sense after a form submission should never appear in a search result. 404 is a system page and is never indexed.