Firsty, them deciding what is suspicious and not suspicious
Not everybody is an employee working for someone. Some people are entrepreneurs, and as an entrepreneur, you can have some HUGE days. I don't need a bank telling me that my successful day where i made $20k+ is suspicious if I want to withdraw all of it. (people have been arrested for making large withdraws before).
Also, banks freely allowing their customers to scam business (via chargeback). Instead of blindly chargingback purchases and screwing over merchants, visa applicants should be required to take a course outlining the risks of credit cards, and Visa should do proper investigations when a chargeback is brought up.
If a tracking number and proof of delivery can be proved, why should the customer be given their money back?
ALSO, i recently looked into banking investment options. It comes across as a way to just make more money off customers. Think of it like this. It's like it's just them taking your money so they can invest it in polyniex. I only tried it out cause my family (who doesn't know about bitcoins) encouraged it.
Do you have any gripes about banks
We all live in different locations so it might not be the same for all of us. First thing I dont like about banks is the unnecessary charges, but not all banks does that and I had to swap to a different bank since my old bank was making unnecessary charges just as ATM maintenance fees while their ATMs are not even well maintained, and there is no money 24/7.
Another thing I hate, just like you said, is them deciding what is suspicious and what is not. When you work hard and genuinely earn a huge amount of money they will tag it as suspicious. But when scammers scam people millions and transact to bank, they are never held as suspicious and bank will not even help you trace where that money got into.