I like to sing in the shower because I'm terrible lol.
I think most people enjoy singing in the shower! It's a pretty widespread phenomena.
I believe it has to do with the way the sound reverberates, also because other people can't hear.
Bathroom singing
Bathroom singing, also known as singing in the bathroom, singing in the bath, or singing in the shower, is a widespread phenomenon. 
Many people sing in the bathroom because the hard wall surfaces, often tiles or wooden panels, and lack of soft furnishings, create an aurally pleasing acoustic environment. The multiple reflections from walls enrich the sound of one's voice. Small dimensions and hard surfaces of a typical bathroom produce various kinds of standing waves, reverberation and echoes, giving the voice "fullness
suppose I am. In a way it's slightly lazy because it means you don't have to pretend – you just have to believe. As much as it's possible to be like that I suppose I kind of do step in and out, I'm not one of these people that can't talk to other people because I'm in my character, but I kind of do stay with the character, yeah. He's always there. It's like marinating something – you're sitting in a marinade the whole