Even the default config is reasonable and instantly usable, so this complaint really isn't very valid. You really can just install either distribution or cabal

Even the default config is reasonable and instantly usable, so this complaint really isn't very valid. You really can just install either distribution or cabal package, run it, and get the work done. On the other hand, there are things, that really aren't going to work just out of the box and are hard to configure. Xmonad has quite a different behaviour than Gnome, and sometimes different from what usual desktop app expect. It might be necessary to create a specific settings for a single application, sometimes. But that's what makes it beneficial. If it were just another bad copy of metacity or kwin-like window manager, without adequate support of EWMH and stuff like it, which is the case of many and many X11 WMs, then it would be really worthless.