Why are the bleachers called the bleachers?

While I was reading about why the 'nosebleed' seats are called such a preposterous name at the ballpark, my curiosity was piqued in reference to another ballpark term that has troubled me over the years. The bench-like cheap seats have always been referred to as "bleachers". I have wondered why my whole life and have asked no less than 3 wise men / gurus, but to no avail. Won't you all please resolve this issue for me and my linguistically starved children?

The bleachers were so named because the boards were bleached by the sun.

The "bench for spectators at a sports field" sense (usually bleachers) is attested since 1889, American English; so named because the boards were bleached by the sun.