We must consider FPS (Frames Per Second) because of the following important fact: A computer can only do so many computations per second.
Games are usually very computation-expensive, so they are particularly bound by this rule.
In games, there are three aspects of this:
- Our update commands take time, and sometimes those slow down our game. (This is usually the least important factor, as update logic can be optimized more than any other aspect of the game).
- The actual monitor has a refresh rate limit (usually 60). Having a game render faster than this is completely worthless, as it is impossible to see changes at a faster rate. This is why games usually cap FPS to 60.
- Render calls can get very expensive, and usually are the main reason why games run slowly. Additionally, game developers have to program for a wide range of hardware, and some of that hardware is relatively crappy, so you have to keep that in consideration. These reasons are the primary focus of frame rate optimization.
Again, this is exacerbated in gaming because most people find a low frame rate actively painful. It looks choppy and strains the eye, so games with poor or unsteady frame rates are often considered "unplayable."