I'd like to take a shot at a quick counter-argument:
1. Tor gets money by delivering a workable privacy overlay to organizations that fund it for such a purpose. The largest funder is the U.S. government.
2. To operate properly, Tor needs a relatively large anonymity pool.
3. The Tor service itself-- while still certainly useful (esp. its hidden services, even for purposes that don't require anonymity)-- doesn't generate a large enough anonymity pool.
4. Tor Browser Bundle adds to the anonymity pool by making the Tor service usable to a much wider audience of non-technical users.
5. To actually attract such users, Tor Browser Bundle must allow Javascript by default so that sites do not "appear broken" by non-technical users who don't understand the intricacies of a low latency privacy overlay.
6. The set of TBB users who view sites with Javascript on by default are subject to a wide variety of de-anonymization attacks which, while generally not trivial nor cheap, put them at greater risk than users who are not using Tor with a browser frontend.
7. Either the U.S. government funds Tor with the intent to use it with a browser frontend, or they fund it for use without a browser frontend. If they fund it in order to leverage the Tor service without needing the browser frontend, then congratulations! You-- the non-technical TBB user-- are the product.
What do you think?