Ok, maybe found a new reason. I'm not sure how the binding arbitration would work going through a bridge.

Without the ability to participate on the Bluesky network without having to create an account with Bluesky (the company), users would have to subject themselves to Bluesky's terms of service, and could have their access to the Bluesky network unilaterally terminated by Bluesky (the company).

...

As things stand, Bluesky has very bad terms of service that every user who creates an account has to subject themselves to. In particular, Bluesky's ToS contain a "binding arbitration" waiver that forces users to surrender the right to sue Bluesky no matter how the company harms them.

Source: https://pluralistic.net/2025/08/15/dogs-breakfast/#by-clicking-this-you-agree-on-behalf-of-your-employer-to-release-me-from-all-obligations-and-waivers-arising-from-any-and-all-NON-NEGOTIATED-agreements

There is no principal problem with bridging to another open system, but Bluesky is not. This is no different from federating with Meta's Threads, which most people on the Fediverse seem to be against as well.

Unless I'm misunderstanding: One-way bridging.

That's very different from Federation.