Roulette question

I know most people here dont play this game, but I used to play it quite alot in my days in AC and I always wondered....

With simple technology availabe for the last 30 years or so, and with a lighted board of past spins already in place ....

whjy could the casino reduce the mental fatigue of the dealers, by having a simple calculator that the dealr punches in , splits quads, staight ups, steets etc....and gets a simple total....with the "work" showing on a lighted board.
Sometimes there are ples of chips surrounding the winning number, and a smart player will say.."pay me seperate" if they cant calculate it in theirhead...which I have found most people cannot. I can calculate it pretty easy in my head,,,,,,but I dotn have to do it spin after spin like the deal does.

Is it that mistakes are more than not, underpay?

There are newer i-deal tables where all betting is done electronically but the wheel, ball and dealer are all still the same.