“Why do I need you? I have a friend who is a very good photographer.”

Being a great photographer is just a small part of being a Wedding Photographer. You have to be calm and highly organised. You have to be able to spot photo opportunities, and set up shot in minutes in all weather conditions. You have to liase with (sometimes difficult) Wedding Venue staff and make sure that you never run over your allocated time otherwise you could be facing a chef with a meat clever. You need to be able to organise up to 200 tiddly wedding guests into a group in a short space of time without being shouty or bossy. You need to keep the bride and groom calm, be pleasant to Vicars, Registrars and anyone else who’s important. You need to have spent many thousands of pounds on computer and photographic equipment and you need to have all the relevant insurances in place.
You then need to be a good, fast editor with an eye for colouring and cropping. Then you need to be a good Wedding Album and Book Designer and a good timekeeper, making sure that the designs look professionally done and arrive on time. If your Uncle Bob is up to all that, then give him a go.