I didn't mean it so much as a physical constraint, but an operational one.
Not everyone wants to (or their policy allows them to) manage TLS certs directly on their origin servers, and some services only allow plaintext HTTP origins, like AWS ALB/ELB. In that particular case it's "ok" because the load balancer is placed inside your VPC, so cleartext traffic is not visible to other customers or networks.
Also, ESNI/ECH would make TLS passthrough problematic.
Not everyone wants to (or their policy allows them to) manage TLS certs directly on their origin servers, and some services only allow plaintext HTTP origins, like AWS ALB/ELB. In that particular case it's "ok" because the load balancer is placed inside your VPC, so cleartext traffic is not visible to other customers or networks.
Also, ESNI/ECH would make TLS passthrough problematic.