I believe you are mixing up NIST ECC curves with Dual_EC_DRBG[1] which is a random number generator based on elliptic curves which is widely considered to be backdoored and they revoked its recommendation (there are much better ways to construct an RNG so it was stupid to use in practice for reasons other than backdoor too.)

The P-series curves are still a NIST recommendation and widely deployed in TLS. The B-series fell out of fashion due to practical reasons.

[1]: https://en.wikipedia.org/wiki/Dual_EC_DRBG