Why are college bball games pre-selected for TV?

It's nice to see that LSU finally cracked the top 25 in both polls today, but what really irritates me is the way that the TV schedule is preset at the beginning of the season and by this time of the year you end up watching 2 garbage teams play each other while marquis matchups and extremely important games are untelevised. It may be difficult for the midweek games but if the networks would decide at the beginning of the week what games to show on weekends, it would be so much better for us (intriguing matchups) and them (ratings). Anyone else think its time to change it up?