I don't think MLB rain-outs are a good barometer for declaring a "ridiculous amount of rain." It'd be more prudent to study rainfall totals. I haven't looked, but I don't think we've had any records in my part of the country, and we've had a fair bit of rain over the last week or two. As for "why," the La Niña effects are expected to continue possibly through June of this year.
FWIW, NOAA states, "Potential impacts in the United States include an enhanced chance for below-average precipitation across much of the South, while above-average precipitation is favored for the northern Plains."
Out of curiosity, I checked 2011 rainfall data for my region (Arkansas), and found this. Only one city is even close to normal (Jonesboro, 93%), whereas the greatest deficit is a scant 44% of normal (El Dorado), with most falling somewhere in between. This seems to agree with the NOAA report on La Niña effects, but to what extent it can explain rain in other areas (such as in northern states), I really don't know. It's springtime, and sometimes it just friggin' rains.