Net worth and annual income are pretty standard questions for verifying accredited investor status.
True, but the whole point of becoming an accredited investor is to prove that you have a high net worth or income and are therefore allowed to spend large amounts on riskier investments. It doesn't apply to people who are trying to buy/sell/trade a few hundred or a few thousand dollars of bitcoin. I could maybe understand if they applied these rules to anyone trading >$100,000 say, but applying them to everyone is utter nonsense.
It seems like Bitstamp's approach is to go above and beyond required regulations out of an abundance of caution, for fear of various allegations, especially money laundering. They seem to have really ramped up their KYC process since 2017, perhaps in response to the BTC-e shutdown -- they were taken down on money laundering conspiracy charges -- or maybe in response to all the SEC and CFTC attention on the industry.
They're not the only ones. Gemini is becoming notorious for closing customer accounts and being overly worried about legal compliance. They even explicitly prohibit mixers in their terms.