I wish people would recognize that the low attendance numbers this year have nothing to do with the team's performance on the field this year, but multiple years of mediocre/disappointing play and fan alienation from the Athletic Department that has resulted in losing so many season ticket holders, as well as some casual fans.
There are basically three categories of fans in attendance:
1) Season ticket holders
2) Fans who decided before the season started which game(s) they wanted to go to and got tickets in July
3) Fans who have followed along and decided as the season has gone on whether or not they might go to a game.
Category #3 is by far the smallest group. For most people, deciding to go to an Iowa football game means clearing the schedule for the entire day, if not more, making travel/lodging plans, and footing the bill on an expensive venture that wasn't previously planned. It's not like making a spur of the moment decision to go to a movie. Because Categories #1 and #2 were so much smaller this year, there just aren't enough Category #3 fans to fill the stadium most games.
It's not surprising, even with the terrific season the team is having, that there are >10,000 tix available for Purdue, the Big Ten game with the least attractiveness going into the season (based on the opponent and potential weather, not to mention many people expected the Hawks to have at least 4 losses by then). Think of it this way - if the Hawka are 10-0, anyone who wants to watch them go 11-0 in person will have a chance.