No real reason was ever given.
Most tribal decks that actually attack with creatures would run it, and nobody likes playing against it, I guess that's all.
The given reason for banning anything:
When a card becomes format defining, it should be banned. The format becomes decadent, devolving into two types of decks: decks that use the card, and decks that are based around beating the decks that use the card.
In Urza's (didn't play, but followed the discussions when Ravager was up for banning), Tolarian Academy decks flourished. They could have near infinite mana on turn 2, with the easy Urza's card drawing and other cards. There were decks that were completely designed around beating Academy. Tolarian Academy is still banned in Urza Block and restricted in whatever they call Type 1 now.
Skull Clamp. If you ran more then 12 creatures, you ran it. No question. Upwards of 80% of decks that would top 8 in pro events would have skull clamp in them. Banned.
If Jitte is legal in a format, you need to maindeck ways to get rid of it or deal with it. It's that powerful a card. Tribal is supposed to be a more relaxed and casual friendly environment. Leaving in Jitte means that most creature heavy decks would have to shell out the ~20-30 tix just to compete.
Not counting tix for things like pithing needle that are the only mana efficient way to deal with jitte.
It's like banning tutors in prismatic: It breaks what is supposed to be casual and fun play. That's why the black Bringer, Gifts, etc etc are all banned in Prismatic, even if they're fine in Type 2, Extended, etc.
In extended, jitte isn't much of an issue. It's a little too slow there, and you have lots and lots of good ways to deal with it efficiently. Especially since Ravager Affinity is still legal, you'll always have some anti-artifact tech main or side.
Even in Standard... Sure, Jitte is powerful. It's singlehandedly lost or won me games. But there are a million ways to deal with it in Standard.
Faith's Fetters is a common. Pithing Needle is widely played. Putrefy is everywhere. Etc.