Last I heard, NoodleDoodle did not want to release the source code for Trezor because RingCT was coming soon. But this could realistically be months away (correct me if I am mistaken there). I think there are many many people (myself included) that don't want to wait months for this to be released. For me and many current Monero users this is more useful than a GUI, to keep our funds secure.

Maybe there is some more work to be done, I don't know. But I do know that NoodleDoodle did this work on his own, and I appreciate that. Perhaps starting a FFS for us to donate to NoodleDoodle will motivate him to release the source code soon.

Update: it seems that the original FFS for Trezor development is still active and funds can be added even though it's been paid out already. If no one has any objections it seems we could just add to that.

https://forum.getmonero.org/9/work-in-progress/265/adding-monero-support-for-trezor