Secondly, as it is an unregulated space, we have instances such as FTX where they were using clients funds which should be segregated. This arguably crosses into fraud, and we do not really know which exchanges have been doing this and which ones have been properly segregating client funds. Coinbase is probably the only one we know for sure as they are an audited US publically traded company.
Finally, we also have situations where exchanges are doing things such as not matching client deposits to their reserves 1-1, or hold those reserves in less liquid investments. This could range from another fraudulent situation to good practice, but leaves them very exposed to situations where everyones wants their money back now.