I've only ever seen them use in short video media about taking foul-tasting TCM, so the want vs need seems to make sense

Yeah I just woke up but it took me a minute figure out what was happening. I thought it was saying that people prefer the bitter medicine, so I was confused why they didn't want to taste it.

Originally, it served a need. Now, I imagine, it serves a want.

It was originally “want.” They became addicted, so now it’s “need.”