Why no reality shows on Fridays?

[AnnaRHR]

It seems like there is a huge overlap of reality shows on Mondays, Tuesdays, and Wednesdays, and the best show on Thursdays (TAR), but why aren't there any shows on Fridays? Maybe it's hard to get ratings, because so many people go out on Fridays, but wouldn't it still be easier to compete for viewers at home with nothing to watch, rather than against about three or four other reality shows?

[marybethp]

Wait until July - you'll have Big Brother on Friday!

It is Tuesday/Wednesday/Friday this season

Then you can have your fill