And that's exactly the point. Just be it's very existence the Tirpitz tied up a lot of forces having to be ready to intercept her. And what if the Tirpizt had just slipped out of it's base unnoticed?
Exactly

Remember just how close Bismark and Prince Eugen came to making it into the open waters of the North Atlantic undetected. Tirpitz could have done the same, especially during the winter with a little friendly (atrocious) weather. Those considerable forces Lusche mentioned could have done one of three things:
1) They could be held at the ready in case the Tirpitz sailed (essentially negated by her very existence)
2) They could engage her after she sailed (and run the very real risk of being negated by her
for real; along with a lot of merchant ships)
3) Or, knowing exactly where she was, they could just preemptively sink her and be rid of the problem.
Besides, it gave the RAF a great opportunity to play with Wallis' nasty bombs.
Considering what the loss of HMS Hood meant to the RN, and to all Brits in general, it's also probably safe to say that the mere existence of Tirpitz was an affront to British moral, so she
had to go. Regardless of military significance.