I guess in part it's become a replacement for "redneck". Watching and listening to some older media, I swear they were using "redneck" closer to how someone would use "white trash" nowadays.

While I still think "redneck" carries a negative connotation in many places, it also seems to be a lot less negative nowadays, And I'm more likely to hear it in the context of self identification or (while somewhat still derogatory) to refer to a kinda idealized version of an unruly and unsophisticated, but fun rural people, and to many, the new redneck stereotype is a sort of role model. Hell, half the "rednecks" I knew in HS were middle class kids who's parents had good job and lived in nicer suburbs than my parents could afford.

There have been some artists trying to take back the "white trash" moniker and use it in a "yeah that's what I am, what about it?" sort of way.

The terms "white trash" and "redneck" have some overlap but they are not equivalent. The former denotes a socioeconomic class while the latter denotes a specific perspective of the world.

There's a lot of "redneck pride", but I don't think anybody has "white trash pride".