Why do you/did you want a PhD?

[GhostsBeforeBreakfast]

This is a simple question I rarely see on here. It might seem obvious at first but I imagine there is a greater amount of nuance between answers than one would expect.
So, especially if you think your reasoning is nuanced, why do you/did you want a PhD in Art History? 
And maybe the smaller question should be, how confident are you that you will be [subjectively] successful upon receiving your doctorate? 
 

 

[lr914]

To put it very simply, I want to obtain a PhD in AH to deepen and complicate my understanding of my field as much as I can, and ultimately contribute to it in terms of research and writing. I have no "practical" reasons, only ones that appear romantic and idealistic in nature, I suppose.