>>4438567 (OP)If f4 "good enough" for you already, you probably wont acknowledge the upsides of faster glass.
Increasing ISO means you are giving up image quality. Tripods are often impractical and cumbersome. Faster glass helps with both.
You also get better lowlight AF performance since more light is able to get to the AF sensor, or lowlight live view, even if you were planning on f4 anyways.
You also get better performance when stopped down, even if shooting at the same f4. Not just sharpness, but stuff like coma, potential for sunstars, CA, vignetting
The amount of bokeh is still definitely different, but the quality can be quite different too. A faster lens might give you better options of more swirly / optical vignette bokeh wide open, that you can stop down to look more normal.
>even f/4 telephotos can do that magic bokeh.Notice how you have to caveat with telephotos, so you understand wide and normal are a bit worse for bokeh at f4
If all you take is stopped down shots where everything is in focus, and often use a tripod, then sure, a faster lens wont help you much.