Your reasoning is faulty. If the average wage for a writer is "well below minimum wage" that doesn't necessarily imply people don't value creative endeavors. It could alternatively imply, for example, that the average creator doesn't produce creative content that others find valuable. With that thesis, if burger flippers do get paid more it could be a result of there being less variance in the value of the work performed.

Even far above average creators, who win awards and sell far above average earn next to nothing. The average full time traditionally published author still earn below minimum wage in the UK (the median household income of full time authors in the UK is above the UK average; most UK authors are able to be full time because of their partners rather than their creative output)

Sure, we can say that still isn't "good enough", but that kinda proves the smaller point that the actual creative output of most creatives is not valued, and at the same time ignores that the main point I made above is that it is irrational for people to gamble on being valued, because the vast majority of "successful" creators as measured by relative rank within their peer group has no realistic prospect of that happening today.

That should be "most UK authors who are full time are able to"...