This isn't always true. On GKE for example, LoadBalancer is very expensive first of all. Second of all, if you use LetsEncrypt such as cert-manager, the GKE load balancer is awful to configure and takes forever to get a cert.

Also by using the GKE load balancer for ingress, you lose out on a lot of things, like password protection, or certain rules you want with nginx.

I've tried my best to stick with GKE LoadBalancer, but it's just an awful experience. Now I have GKE to load balance traffic to nginx-ingress, the level 3 load balancer is just not flexible enough and in general annoying to configure.