While all kinds of cool sensors are nice, I don't think they are the real reason driving the push towards remote weapon stations/unmanned turrets. It's force protection. A tank commander driving his M4 down the streets of Leipzig in WW2 was just (if not more) likely to get drilled in the head by a sniper as is an M1 TC in Afghanistan. The difference is that today, any fatality has a political impact far beyond it's tactical or operational impact. People freak out now when they here that 2 US serviceman are killed in one day in Afghanistan. God knows how they would deal with something like D-Day today. In WW2 it wasn't worth protecting a TC - I believe only the Germans came up with a remote controlled TC machine gun for their Hetzer tank destroyer.
(on a semi-related note - the War on Terror (Iraq & Afghanistan) the US has averaged about 2 fatalities a day. Vietnam it was 26 a day. 45 a day in Korea, 416 in WW2, 279 in WW1 and a whopping 599 a day in the Civil War! I wouldn't want to even guess the number of fatalities per day the Germans or Soviets took in WW2. *Shudder*)
The US military (and I suspect most western armed forces) has developed a bit of a fetish about force protection because of this. Especially after all the bad press about unarmored vehicles at the beginning of the Iraq War ( I never understood how using an unarmored HMMWV as a COMBAT vehicle in close terrain could possibly be considered a good idea...) Now don't get me wrong - as one of those being protected, the increase emphasis on keeping me breathing is nice most of the time. Some times it gets a little silly though - like loading people up with so much body armor that they can only pant and wheeze while they watch Taliban in robes and flip flops run up the side of mountains laughing at them (luckily the Army has acknowledged this problem and is issuing plate carriers to infantry in Afghanistan instead of full body armor).
So while many TCs would like a turret that lets them stick their heads out once and while to see whats going on, the Army doesn't want to risk them getting picked off and end up another bad statistic to get explained to an increasingly war weary public.
Plus fancy remote thingees make defense contractors more money. Am I a cynic or what?
Then again, and playing devil's advocate, if a bad guy drills you right through the scone because you were heads out, you'll have a much bigger problem than muddy optics.
Many optical sights even drivers vision blocks have wipers to clear crap from lenses. The ability to look at something a long way off with decent magnification, image stapilisation so the image isn't useless whilst the vehicle is moving and that the image is available day and night via thermal or Ii technology has a lot going for it too.
Perhaps the ultimate combination would be something similar to the F35's DAS - whichever direction you look in the picture is presented as though you were able to see right through the vehicle.