Once you GM some more games, however, you'll start to realize how useful the ITS is when you need to do audits for a scenario (especially Seasons 4 & 5).
The most common reason I've seen is whether anyone has a Lissalan Rune or Brand. There are several scenarios where that matters, and where there are detrimental (or beneficial) effects to players that do. Auditing let's the secret remain in place until it is revealed.
How is it easier to look at the ITS than the character sheet?
Especially since these items do NOT have to be on the ITS (some aren't purchased with money and some were acquired before the ITS became mandatory)
As far as I'm concerned the ONLY definitive record of what a character has is their character sheet. Even in the ideal world where all players keep their chronicle sheets and ITS rigorously up to date that would be true. And it most certainly is true in the world that I live inn where lots of players paper work is more than a little imperfect.