If you have, or will, ever go through a “redesign” of a website, chances are very high your webmaster is going to start fresh. They are going to use the names THEY are used to using to name pages. For example, is it contact, or contact-us. Is it About, or About-Us. These seem like minor decisions with no real consequences.
Until you move a high traffic website. And all your high traffic website pages no longer EXIST, because your webmaster renamed everything. Imagine putting a huge print ad for your new retail store but by the time people drive to the store, you’ve closed up and moved? Not good.
Let’s say you have a page called “pinkly.” Pinkly gets a lot of traffic from Google searches and it really makes you happy to rank so high for that word! You give your webmaster the content for Pinkly, or s/he grabs the content themselves, and decides to call it something different. They don’t think anything of it. Afterall they aren’t in your profession and have no way to know what “pinkly” means. So they may name it about-pinkly, or maybe it’s a form of therapy treatment, so they create a new page called treatments, and they stick it inside there. The point is once they set up your new website, all those people who Google and find your website under “Pinkly” will open a BROKEN link. It’ll give them a web error!
A really good webmaster will either keep the same page names, or at least attempt to forward old pages to the newly named ones. But this is not common. Or, it’s very time consuming, which results in a large invoice to you!