I wouldn't know why "it stinks"; the Broker doesn't get your money either - at least not if you trade via an online broker. It may be different if you use one of the "Full Service Brokers"; from memory, however, I seem to recall that they too had direct debit/ credit authority to my account, and they would transact not on the day I made the phonecall, but like now, on "T+3".
So, in reply to GLK's question: If you're using an online broker, not only are the brokerage rates a fraction of what an FSB would charge, but as soon as your buy order is reported as filled, you own the bundle; if you know you won't have the cash in your bank account 3 days hence, you better pray that they rise and you can sell them at a profit on the same day. Or you see them rise and hit resistance, so you decide to take profit immediately. Three days later, you will find your account has been credited with the difference, minus two lots of brokerage.
Some brokers (Westpac is one of them) even accept the value of your share portfolio as "collateral" allowing you to buy - and sell on the same day - up to the combined value of your current cash
and portfolio balance.
You can take advantage of this feature (which may also explain why I don't agree that it stinks)
Say you have found a stock that moves quite regularly a few cents down and up again inside an ordinary day. CFE is a good example: starts near previous Close, drops back over lunchtime, then recovers a couple of cents. Buy 10,000 at an Intraday Low and sell a cent or two higher. For every 10,000 shares, one cent difference pays you $100. Subtract the brokerage - most onliners will charge no more than $25 one way. You do the Maths
I trade through PariTrade and can buy and sell the same stock a dozen times in a day and they still charge me only one brokerage per contract note: $25 minimum, 0.1% if the total amount is above $20K. Other onliners have similar offerings.
The crucial point is: Buy and Sell orders are treated exactly alike - cash settles on Day 3.