Because TLS doesn't operate at TCP level. It encrypts the payload carried by it. TCP (and IP) headers (source/dst IP, port, flags, etc..) remain unencrypted.

Because TLS doesn't operate at TCP level. It encrypts the payload carried by it. TCP (and IP) headers (source/dst IP, port, flags, etc..) remain unencrypted. On the other hand, IPsec operates at IP level (which can be tunneled over a clear IP/TCP layer)