From what I've read, fruitcakes are usually covered in both marzipan and fondant (sugar paste) but are regular cakes as well? If so, is this only in the UK? And is this still a current practice? 

I understand why a fruitcake would be covered in both..but why would one do this with a regular sponge like cake?

I know a lady is somewhat new to cake decorating - and who gets a lot of information/ inspiration from mainly UK cake decorators/books-and she told me that she always covers her (non-fruitcake) cakes (sponge, chocolate etc) in both marzipan and fondant. When I asked her why she would do this for a non-fruitcake cake, she told me that's the way it's always done. 

hmmm I've never seen this done before..so just curious if this is an outdated practice or just an English style to cake decorating?

Why would someone do this? Isn't it a bit redundant to use both on something like a vanilla cake, or a mud cake?

Hello cakefat, sometimes a baker may use both and I am sure  it is to make the cake look really smooth, however I am not sure if you do that with light and  spongy cakes. When I bake chocolate I use ganache for icing.

Well I'm from the UK, and my grandma was a skilled cake baker/decorator, she only ever did marzipan on fruit cakes.