Why? Because this stuff is in the kernel and thus harder to see? I don’t expect moving it to userspace to reduce overall complexity —- just move it elsewhere.
Because it’s in the kernel you aren’t exposed to all the knobs. There are hundreds of parameters controlling Linux tcp behavior. Even experts overlook some aspects. Hoisting this up into your application makes it visible. Why should there be a system parameter that limits the accept backlog of your server, silently? It makes no sense.
Because the people who wrote it think it's better being a bit more inaccessible in the kernel so that regular users don't shoot themselves in the foot thinking they know better than the designers what the values should be. The people who know what they're doing will be able to set the parameters regardless of where they're hiding.
