I know the Tiger Pool Tour (Northern Virginia) is dead. The last tournament was April 2009, and their web site (planet-pool.com) finally disappeared about two or three months ago.
There is no surviving tour in the Northern Virginia/Washington DC area, although I did see some posts from someone running a one day tournament near Baltimore that looked pretty good.
As to why it folded, hard to say, but I have a guess. You had a lot of the same players playing regularly, with a small group of the same guys usually cashing and the rest of the players almost never cashing. My guess is that the non-cashers got tired of contributing their entry fees and stopped showing up.
The tournaments had pretty good turnouts in the years it was running, but I think that was slacking off at the end. I know several guys who played in the tournaments, two of them pretty well. One of them dominated the tournament and regularly placed first or second in it's last couple of years. The other is a solid 7 in TAP, but always finished in the middle of the pack and never cashed. He was one of those who eventually gave up.
I also know the person who ran the tournaments, but not very well and didn't get a chance to talk to her about why it died. I'm guessing she just wasn't making enough money to continue.
Now to comment on the value of a bunch of small tours vs a few or one comprehensive and well organized tour. This has been discussed numerous times in this forum and on several pool blogs. I agree with the majority that it is not helping the sport at all. I am one of many who would love to see just one well organized, fair, and reputable U.S. Pool tour with both amateur and pro level events available throughout the country.
It's not that it hasn't been tried before. Either it wasn't done right or the money just wasn't there to make it successful. Most pool players believe it is the latter.
Still, I wish someone with some startup cash, guts, a hard work ethic, motivation, and the right industry connections (Mark Griffin?) would step up and try to get this done right. Clean out all this trash and develop a quality reliable tour.