"Payment for order flow sort of created the zero-commission retail-brokerage model, but it’s not really necessary anymore. You can run a profitable retail brokerage on net interest margin, without charging for trades at all."
So what everyone should be complaining about is not PFOF, but "net interest margin". In other words everyone should be complaining about the brokers not paying enough interest on the cash balances in the brokerage accounts.
I transfer cash in once I've decided to trade and the brokerage usually holds it for a max of a day or two until the trade actually executes (say I am buying an index fund where orders today are executed tomorrow). The only time there has been cash for longer than that was when I know I needed it (a week or two before buying my first place) so I didn't want to risk a stock market crash etc.
Some people use a brokerage account as a checking account. Most don’t. Interest can also be earned on lent securities.