The hits aren't consistent, the damage is lacking, the super is harder to combo, and Chun-Li isn't very ex reliant are a few reasons I can think of as to why people dont like it. I also think if you're worried about anti-air, kikousho does a better job
Not changing my sig until Soulja Boy challenges me to a rap battle
The reason everyone beats off to SA2 is that it covers a huge, huge deficiency in Chun's game. She has no real combos or danger to her without meter (for SA2), so without that super at all the opponent is free to just bully her all day. Worst-case scenario you get thrown.