Regardless of fuel costs; the main reason for IMAC was the amount of competitors. When it cost $30 to fly a contest and about $100-200 to get there and stay in a hotel I'd rather fly against 15 other people than 3-4.
That's a shame, but maybe you'll see the situation change over time. Other areas have a really healthy turnout for both Pattern and IMAC. It's pretty much equal in the Northeast for the number of contests as well as the number of participants. Losing fields is the larger concern in the Northeast. This is where getting the noise foot print down as well as keeping the overflight area to a minimum can help. It's not easy either way.