I've supported bitlocker in corporate deployments. I have also spent some time in independent repair shops. I have little confidence in users to supply a bitlocker key, let alone even know what one is. I anticipate a lot of "what? I already gave you my password."
You can still mount it to another machine if you have the key. It's an extra layer of pain in the ass, though.
I don't use an M$ account so if your key is backed up to the cloud (aside: can't wait to read the headline about when that gets breached) I don't personally know offhand how difficult it is to extricate your BitLocker keys from Microsoft.