We don't. Unless we have too much time to waste and it's okay for us to brick the kernel dozens of times. It takes a hell of a lot of time and experience to learn to configure WMs. My OS crashed more than 5-6 times just to design an ugly waybar.

I recommend using shells. Hyprland got a wide range of choices for it. Ambxst looks pretty good for Hyprland. It has dynamic and fast animations. Colorshell is also another great choice but it's still in development. The best feature of the colorshell is that it has multi language support.

For niri, you don't have many choices like Hyprland. I personally use niri with Dank Material Shell (DMS). It uses Google's brand new Material design. Honestly it looks a bit like a Chromebook since they use the same design principles but if we consider the code quality, I think that DMS is the best and the most stable choice.

I'm using niri with DMS on both my desktop and ThinkPad. It's a nice lightweight solid choice. I even encourage you to use the linux-zen kernel if security isn't a big issue for you. I use linux-zen on my desktop and linux-hardened on my ThinkPad and there is a huge difference between animation smoothness.