I always use plumbers as an analogy too. What is it about them?
Roger is spot on. The "showcase" approach is particularly galling, and I'll occasionally respond with something along the lines of "That'd be marvellous - my work's only been seen in the likes of The Sunday Times, The Beano & Dandy, and the odd national daily newspaper so far. So, how many copies does the Ferret Fanciers' Gazette sell each month then...?"
Cartooning and comics has been my job for over thirty years, and it does occasionally get boring, believe it or not. I recognise how lucky I am though, and that I could be doing so many other things to earn a crust that I'd hate within a very short space of time. But that just makes me lucky - not a mug! That said, I enjoy unpaid work immensely when I choose to do it, for a good cause, or people I love/like. But I can't remember the last time I drew anything purely for my own amusement or pleasure. I suspect I was too young to drink beer though.