Why is it not as fun? It's just a different kind of game. There are plenty of tactical shooter or sniper games that go through a lot of effort to model the ballistics (like the Sniper and Sniper Elite series), as well as pretty much every tank and naval game. The Battlefields weren't as fast-paced as UT, but they made great use of ballistics for everything from sniper rifles to RPGs... added more skill to the game.

Even Unreal Tournament itself had some basic ballistic guns, like for the alt fire of the flak cannon and biorifle.