Is it really necessary for real productivity that we have instant transfers and trade on crazily priced equities? What part of the real economy requires any of

Is it really necessary for real productivity that we have instant transfers and trade on crazily priced equities? What part of the real economy requires any of that? I'm doubtful. I wonder what a Tobin tax, and possibly even some kind of ban on high speed or even fast trading would do? i.e. throttling limitations? Or something to slow down the trading? Would it affect the real economy and would the financial sector be prevented from creating value? Or would it just mean some casino aspect of the operation is limited ... I'm not suggesting we actually do that, because it's fine if people want to do those things so long as it doesn't affect the real economy with negative externalizations. But I wonder if it would be better for the system as a whole.