Why are trading floors so low in the bank buildings?

Cheaper to keep cool with all the monitors. Also they're usually just larger spaces (200 west - goldman e.g.) and buildings taper as they get taller 

Traders don’t need a view

My guess has always been that the trading floor uses the most electricity out of the entire building and so maintence is a lot easier

I always think it’s due to that management thinks even if all elevators are down in the building, traders can still climb stairs easily and quickly and do their job!..

Bit of a wild guess here, but maybe to do with traders being able to get out of the building easily (separate lifts/stairs etc) if there was an immediate need to relocate to a DR site. Its not spoken about much but many if not all IB’s have DR sites dotted about.

I always thought it has something to do with what happened during 9/11 then trading floors moved to lower levels

so you don't jump 

Traders have extreme cocaine energy, you can not expect them to sit still in an elevator.

Since traders typically have acrophobia. Just kidding, to be closer to the infrastructure that is usually plugged at ground level.