In a time where you can get sued by anyone and the age of trial by social media and biased news, sometimes not doing anything is the better self-serving option.
Yes, and you are especially at risk if you report a black person. For example, Amy Cooper did not act well, but she did not deserve national vilification and losing her job. If you wrongly report a white person, it won't become a national story. In this case the rapist was black.