Why?
I use Schwab, Fidelity, E*Trade and IBKR. Each of them has advantages and disadvantages.
I had a put expire on Friday. B”H the stock took a dip on Friday, so I was loosing less than I thought I would. In the past, at the close, the brokerage house would (from my point of view) just make the calculations and I would have the profit or loss as a transaction.
(ie The strike price of the put is 20. The stock closes at 15. I get $5. )
Schwab actually had my account SELL the stock! So I was now holding a short stock. That may have been my mistake, although Scottrade, Ally, and TD never did that.
The part that is unmistakably Schwab’s fault is that I couldn’t find the transaction listed until after close on Tuesday. I didn’t realize I was holding short stocks. And by then the stock had gone up again. Increasing my loses to buy to close out.