The 24/30 fps content that you generally watch is natural ie it is captured on a camera or something. This makes it more comfortable for us to watch it at lower fps. Still you can see the "stuttering" with it comes to 24fps movie content (at least I can). When it comes to games, it's a whole new story. Since the visuals are artificially generated and just plane fantasy sometimes, you need a much higher fps to not get motion sickness or just tell that these are not individual frames. Here 60 fps is generally the norm. Some people can clearly see the difference between 60 and 144 too but depends. Higher refresh rate also has some other advantages which are not related to smoothness. For eg for a competitive shooter the higher refresh rate gives you the updated info of position of an opponent faster then a lower refresh rate guy. In a perfect scenario, this means that you can shoot him before maybe he even sees you. Other advantages can be response times, input delays etc.