Actually rain occurs quite a bit in baseball, especially in Florida & Seattle. It just doesn't always cause delays or cancellations. If its a light drizzle they can & usually will play through it.
Don't you find it kind of dull with the same constant fair weather in past iterations of The Show? Wouldn't it be more interesting to play a game where theres constant worry about the weather on cloudy or overcast days/nights? Then if it does happen to start raining hard enough to cause delay, that's when bullpen strategy comes into play if your starter is still going strong at the time. It's all about variation & ways to keep every single game interesting in more ways than just on the field play.
Now if Sony implements the weather conditions like 2K did, then I'd agree with you. They did a horrible job with those lines falling from the overlays supposedly resembling rain. I don't think that'll happen with Sony though. Especially since Kolbe & Chris have mentioned in the past that they're holding out on weather till it can be done properly. Well you'd think with the power of the PS3 that would no longer be a problem.