for example, the san diego game right now is clear skies and sunny, why are the lights turned on? does it even make a difference?

actually, i think i might've figured out the answer to my own question. is it because it takes a long time for the lights to warm up and light at it's maximum brightness? and in order for the game to have the the best lighting by the time it gets dark, that's why it's kept on?

it makes a huge difference... ok it doesnt really.
depending on the stadiums.

the baseball stadium is said to have a rule that there be no shadows on the stadium, so if there are any blanks, thats why there are lights

in the football domes light is important only for cameras and video makings
thats why highschool football doesnt have any lightings in the daylight
but you see nfl games are spotlighted

basketball...
well thats pretty much the only source of light basketball gym/centers have
considering its covered

I believe it is because the lights take so long to warm up to full light and the game will finish in the dark.

The stadium owners want to waste even more bling.

So everybody gets used to them.