The whole input mains wiring thing is a bit of a nightmare for international manufacturers like Marshall & Vox & Fender. What you can do in one country is often not permitted in another. So if you have multiple models going to many different countries and each has a permanent power lead attached then each item would need to be wired to the country of destination, which is a real PITA!!! Probably why the 'figure 8' for double insulated and IEC socket for Earthed devices on the back of amps became so popular so quickly as all those colour and wiring issues are dealt with in the separate power lead that is thrown in with the product packaging, so therefore the product itself can be made in a standard way for world wide distribution right at the factory of manufacture.

While having the power switch before the fuse is safer in that there will be no power on the fuse socket if you turn the device off while you change a blown fuse there are some manufacturers that don't do it. To save a few cents in wire and to not having mains power going back and forth from the front to the back of a chassis there are devices out there that are wired to the fuse holder first and then to the main power switch. While they are not 100% correct they are also not illegal in most countries, however they are less safe. And which side of the fuse holder is connected to the incoming mains contributes massively to the eventual safety of the device user.

I once had a old VOX amp come across my work bench that a guy had bought in the UK and brought with him to Australia when he emigrated here. Apart from the UK plug it had the standard UK colouring of Black as active and White as Neutral and a solid Green earth on a fixed cord to the amp. He wanted it change to an AU plug as the little adapter he was using to power it was falling apart. It was an easy fix but the whole flexible lead had to be replaced so that it complied with the AU colour scheme for mains powered fixed cord portable devices.