I'm not sure what you mean. HAProxy has always been a layer 4/7 load balancer and has indeed never been a web server.
NGINX historically was a web server (an excellent one) which has evolved towards proxying and a bit of load balancing. But in terms of LB features it lacks a lot, just like you wouldn't try to cross-dress haproxy into a web server in any way. It's true that for many quite simple setups nginx is often enough and saves the admin from having to learn another tool. But when you start to handle tens of thousands of domains, need to perform DDoS protection, handle thousands of servers, perform inter-DC state synchronization , stream tens of Gbps of traffic, or perform advanced actions on health check status change, it's not well suited aanymore. It's still the best web server I know, and many hosting infrastructures combine haproxy+varnish+nginx together, taking the best of each and deliver unrivaled quality of service. The beauty here is that these 3 best components in their respective categories are all free to use so there's no reason to have to choose between one or the other, just use all 3 and be happy!
NGINX historically was a web server (an excellent one) which has evolved towards proxying and a bit of load balancing. But in terms of LB features it lacks a lot, just like you wouldn't try to cross-dress haproxy into a web server in any way. It's true that for many quite simple setups nginx is often enough and saves the admin from having to learn another tool. But when you start to handle tens of thousands of domains, need to perform DDoS protection, handle thousands of servers, perform inter-DC state synchronization , stream tens of Gbps of traffic, or perform advanced actions on health check status change, it's not well suited aanymore. It's still the best web server I know, and many hosting infrastructures combine haproxy+varnish+nginx together, taking the best of each and deliver unrivaled quality of service. The beauty here is that these 3 best components in their respective categories are all free to use so there's no reason to have to choose between one or the other, just use all 3 and be happy!