Why is a stock market crash so bad?

Many folks speak about potential stock market crashes when central banks raise interest rates. I am not a graduate economist nor do I pretend to understand it, but I am definitely curious about what's happening because it affects me. I have two questions: Why is the FED/ECB/whatever raising interest rates bad for stock markets? (I am aware that this is an assumption - my information could be wrong.) Why is it so bad if the stock market crashes? If nobody wants shares of companies A,B,C or everyone is in rush to sell shares of companies A,B,C, does it mean that the companies should stop their operations? Does it mean no one would buy the goods/services produced by these companies? In 1929 the stock market crash resulted in huge unemployment. I don't understand why. I understand why is bad for shareholders, but they are the once gambling in the first place. Everyone take these consequences as a common sense and no one really explains why is it so.