Answer:
In the beginning, most fossils that were found were of soft bodied animals which led to their decay quicker. Additionally, the movement of the tectonic plates destroyed the fossil records. Due these reason, a lot of fossils that are found are unfamiliar to the scientists.
But with time, as the scientific knowledge is increasing, the processes to deal with fossil operations has become more precise to avoid damaging the fossil and also figuring out their origins.