There's a poster below that provides a more reasonable use case for TPM. Headless server where asking for password on boot is undesirable (eg after a power failure)
A TPM provides hardware-backed bruteforce protection which means even an easy passphrase can be made secure as the number of attempts is rate-limited by the TPM (to a level much slower than even the hardest hashes).
People tend to trust them more because they belong to them, not Microsoft, or Hollywood, or the board manufacturer.
A YubiKey/external TPM in comparison has no way to know whether it's being fed true PCR readings from the host or fakes from a malicious attacker, so at this point it will be no different (in the context of full-disk-encryption) from just having a dumb USB storage device with your LUKS keyfile on it.