Firstly, BitLocker can be used with or without a Trusted Platform Module (TPM) chip, so Intel TXT is not necessary for Bitlocker without TPM. TPM is a dependency of TXT but not the other way around. The TPM is where TXT will store the measurements - hash of components - of the platform.

Is Intel Trusted Execution Engine Necessary?

The Intel Trusted Execution Engine driver enables the system to boot securely and is required for system security features.

Is trusted execution technology important?

This is essential in that if the platform cannot be protected, then the data it will store or process cannot really be protected. At a minimum, this technology provides discrete integrity measurements that can prove or disprove a software component's integrity.