Board Thread:Theories and Speculation/@comment-33286580-20180609133213/@comment-734582-20180609174412

LegionZero wrote: Most Uchiha develop a fighting style by the time they are older so they dont necissarily need to copy an opponants techniques, but that doesnt mean they cant. The thing is, the Sharingan can retroactively copy any ninjutsu it's seen. it's just, it rarely is necessary. It's been shown over and over again that Ninja prefer a few techniques they practiced to perfection, rather than dozens of techniques they can barely use. Even Kakashi, who famously copied many ninjutsu, only uses the absolute best he's copied, and even then only situationally appropriate ones (e.g. he doesn't go around creating mist in every encounter).

Or as Itachi liked to say, every ninjutsu has it's weakness. and if you're only using ninjutsu you copied, chances are your opponent may know them better than you do. using copied ninjutsu doesn't come without it's risk.