It is an easy habit. The rota is made in Word, saved as a PDF, and put on the website as a link. Everyone involved can see it, so it feels like the job is done.
The trouble is that a PDF is a photocopy. It is a picture of a document, and the website cannot really see inside it.
A phone does not like PDFs
More than half the people looking for your service times are standing somewhere holding a phone. A PDF opens in a separate viewer, at the wrong size, and has to be pinched and dragged before a single line can be read. Many people give up at that point.
Google reads pages, not attachments
When somebody searches for a church service near them on a Sunday morning, Google is matching words on pages. Text sitting inside a PDF is largely invisible to it, so the one page that answers the question never appears.
What to do instead
Put the times on an ordinary page, as text, with a clear heading. Keep the PDF as well if the rota is genuinely useful to print. It takes about twenty minutes and it is the single change that makes the most difference to a small church website.