Fishmongers and supermarkets will fillet fish for you, but it can be a useful addition and a handy skill when necessary.
My local supermarket had a batch of whole salmon which were often in the ‘reduced’ isle because they were too big for most people and no-one knew what to do with them.
I bought them regularly at a very cheap price, brought them home, filleted them, cut them into pieces and froze them for later. It saved a fortune and kept us going for about 6 months in salmon fillets!
Cod fillets are another cut of fish that is often sold with the skin still on. It doesn’t tend to go crispy, so I like to remove it.