Because I don't think the storm is going to be that bad in Orlando. I am very disappointed that I will miss out on probably two days at the parks due to rain and wind, but I'm not concerned at all about the integrity of the buildings I will be at.
I also am travelling with just my girlfriend. We are both young(ish), and do not have children. We plan on taking 10-20 gallons of gas down with us (we are driving) in case we can't find any. Also plan on taking a few cases of bottled water and quick-to-eat meals on the chance supplies at the resort are low.
They won't really go into their hurricane policy until a Hurricane Warning is posted I believe. That will likely happen late tomorrow or possibly Friday. That's when I will make the final call on whether to go or stay.
I think the most likely impact to Disney World is comparable to what Matthew did... which was bring some rain and wind but nothing extraordinary. To be quite frank, I don't see this being any more dangerous than when a nasty summer thunderstorm with a ton of lightning pops up while people are in the parks.