And why would the Emperor, a guy who shoots lightning bolts out of his fingers need a lightsaber? It’s just stupid.
'Cause as AOTC showed us, lightning can be simply blocked by positioning a lightsaber in front of it.
(Obvious sarcasm, is Obvious.)
Wouldn’t it be much more creepier/scarier/effective if Palpatine would kill the Jedi who came to arrest him by simply breaking their necks with his mind and slowly going away smiling?
Or turning them into crispy critters with his Force lightning. Either would work.
I think it was The Last Command which first showed that Force Lightning could be blocked by a lightsaber. Timothy Zahn has many strengths, but grokking the Force is apparently not one of them. I believe that Lucas got the idea from Zahn, since he lifted much of the plot of Dark Force Rising and used it in AOTC, to much lesser effect. For example, there is a subplot involving an artifact of unknown design, a princess under threat of capture or assassination who must travel under guard to multiple planets, and the suspicious deletion of information from the archives on Coruscant.