I don't know, but one of the reasons could that they had 3 stadiums with Saitama Stadium and Yokohama Int. Stadium and Kashima Stadium in the Tokyo area.
The main reason was that there wasn't a stadium that was capable of hosting World Cup matches in Tokyo. The National Stadium is old and would have needed significant upgrades, which probably would have cost more than a new stadium, and they hadn't begun construction on Ajinomoto at the time of the bid. For the '18/'22 bid though, they will propose Tokyo as a host city, and the bid is actually dependent on Tokyo winning the 2016 Olympics, and using the new Olympic stadium as the venue for the final match.
It was too bad Tokyo didn't host any matches but question is if they get the world cup in 2018 or 2022 will Tokyo host any matches?
The rest of the sports world would be reluctant to give the 2022 or 2018 WC to Japan so soon after they had hosted the 2016 Olympics in Tokyo. Moreover they want to host 2015 or 2019 Rugby World Cup, the second largest WC event in the world behind the soccer WC. I think the possiblity that we will host 2018/22 WC or 2016 Olympics is slim.
If the economic downturn continues (or even if it doesn't), though, this type of package deal might be more common. Anyway: http://au.sports.yahoo.com/olympics...6/japan-world-cup-bid-rests-2016-olympic-vote With the 2016 Olympic Stadium, Japan can host the World Cup without building a single new stadium. That's a big advantage, considering the difficulties South Africa and Brazil in getting stadiums and infrastructure ready.
http://hochi.yomiuri.co.jp/soccer/etc/news/20091004-OHT1T00269.htm JFA president Inukai wants 80,000 stadium in Tokyo to host 2018 or 2022 WC final!