Approximately a quarter century of editor UI muscle memory in everyone who's used Flash/Animate professionally. And a quarter century of people being used to the precise quirks of how Flash/Animate organizes the parts for a cartoon. And a quarter century of source files in a private format that can only be read and understood by Flash/Animate.
replyWho has authored anything they actually cared about using Flash in the last 15 years?
replyI don't know Animate - is it basically Flash Updated (I've read here that Adobe kept some elements of Flash in Animate, but it is unclear what).
Also, there are non-Flash players for .fla files (not editors, however).