Because Lucas himself never intended for any of these characters to be anywhere near as powerful as novels and comics try to portray them. Order 66 or Jango Fett being a credible threat makes no sense if these guys can move at sublight speeds.
As far as Lucas was concerned, nobody does; everybody is pretty much mid/upper tier street level. Hell, even basic mach speed is not really on the table. It's the novels, games and other adaptations that try to push the limit here.
Well, mostly because Lucas changed his mind about a lot of things. During making the OT he stated that Yoda and Palpy weren't the kind of Force users that wielded lightsabers. Their knowledge of the Force and their powers were different. In the PT he is the one that turned them into superheroes, which clearly they weren't meant to be when Lucas made the OT.
well, in story he was caught up in his own hubris and didn't notice Vaders turmoil while trying to KILL HIS SON
in the real world Lucas didn't have the tech to make the Jedi/Sith as powerful as he would have liked, hence why Dooku, a 100 year old man was able to do flips off of balconies and beat up on two young, powerful Jedi but old Ben could barley parry a blow from a stiff cyborg.
We... we all know why he couldn't. We also know why he claimed he didn't. This would have sounded a lot different had he the money and technology to pull off a special-effects bonanza PT-style from the get-go.
Would have sounded more like: "Special FX are the key to all this. A sci-fi story without special effects is a pretty boring thing."
He's good at spinning his limitation into credit.
__________________ I'm not going to lie: I despise children. There, I've said it.