The Need to Create While Working in a Creative Field

How do you justify creating outside of work, but also justify being paid for what some see as a "hobby"

As someone who works in a creative field, one would think I would want to come home and do some math equations or something; not want to create more. But, I find creating outside of work helps keep my mind excited and sharp. 
This same feeling is true for many others working in the creative fields. Some try to take advantage of this feeling by asking creatives to do their work for much less than living wage or, heaven forbid, no pay at all. It is hard to explain the need/want to create combined with the necessity to be paid. Many people who have jobs in such fields as health, education, etc. get their creative fix through volunteering in creative areas. It is hard to explain that since the creative field is my job, I won't work for free. This is not to say I won't volunteer for a niece's school play, but if the position is more of a full fledged job than a few hours of pinning hair up, it should come with pay. 
But what of this need to create outside of work? How do I justify doing something creative without being paid? I tend to find creative outlets outside of my creative job field. As I am a costume designer I lean towards interior design, writing this blog, and drawing (I know costume designers draw too) to sooth my creative itch. I create interiors for myself and draw things I choose based on feelings, prompts I find, etc. 
My creative outlet also doesn't take up a workday's worth of time. I am not required to do it or be in a specific place for a strict amount of time. If I was, it would be a job and I should be getting paid a living wage to be there. 
While writing this blog I found if very hard to articulate my thoughts on the matter. This is something that wasn't discussed at school. As creatives we all have this drive to create, but when you pair it with our chosen jobs in what society calls the creative field, some easy to distinguish lines in other careers become muddled. I rarely (truly never) have an itch to perform surgery on someone, but a surgeon can have a creative spark in photography or sewing. Some see what I do as a hobby, because it is for others. It is very difficult to illustrate for those who did not go to school or costume design that I too have an expertise in something.
This article was meant to be an exploration of how professionals in creative fields feel the need to continue creating outside of their work and fields, but has turned into a little bit of a fair pay stream of consciousness. I hope it sparks some creative juices in you one way or the other.