Alternately, they don't want people to rely on abandonware for security.
Also, despite the conspiracy theories of backdoors I'm not aware of any bitlocker exploits that work on TPM + pin, which is the intended "secure" configuration[1]. All exploits rely on TPM-only (ie. ez-mode), which is basically the security equivalent of running https/ssh without certificates and blindly accepting whatever keys shows up.
[1] https://learn.microsoft.com/en-us/windows/security/operating...