One reason for the success of the American Straight Pool Championship the last 3 years is that it was played the week before the US Open 9-Ball Championship and just 2 hours down the road from it. So players from outside the USA could play both events on the same trip.
That's definitely one reason and as Bob mentioned: lower entry and considerably more added money.
Another benefit to the players when compared to the world event is much lower expenses. Plus everyone likes Peter Burrows. The same can't be said for Charlie Williams.
It's even more attractive for spectators.
Free addmission
Free streaming
Low expenses if attending in person
Possibly the most talented fields ever assembled
I'd predict that the American will continue to get better and better, and wouldn't be at all surprised if the Worlds disappears in the near future.
If you do decide to attend the American 14.1 championship try if possible to get there a day early.
Greenleafs poolroom in Richmond has an exhibition match the night before the tournament starts, usually featuring Hohmann and another top player (last year was Mika). The venue is superb, the atmosphere is electric and it's a memorable evening.