Maybe it's just a difference in how people perceive the word contrary to its actual definition.
I have come to hate all that sassy represents because every time I see sassy, shallow behavior ensues.
It's like a loose cannon, someone flitting about, sassing with all those one-line zingers, very self-centered and involved. Neither you nor they know what they're going to do next but it's all about them.
What's so interesting about a character like that? I don't get it.