We find many dinosaur fossils because there were so many dinosaurs over so long of a time. The actual events that lead to a dead dinosaur fossilizing and then having it be in a place we find it all these years later is astoundingly rare, and speaks to the scale of numbers we are working here when we find these fossils. There were probably orders of magnitude less humans over orders of magnitude smaller amounts of time in question here than say, dinosaur finds. Then you have the issue of early humans generally settling in places that are poor for long term preservation, like along shifting coastlines. The fact we find so many hominid remains in places like caves isn't really because that's where people spent a lot of time, but that these people were all over the environment and of all the places for their remains to end up, in the cave is a good place for it to not only survive the elements but to be found by spelunkers in modern times. Most people probably died and left evidence of their life in places exposed to the elements or to time.