I have run events (not gaming) in the past, and large urban areas present problems, primarilly COST.
Holding an event in a place like Lancaster (that is pronounced LANK-aster, not LAN-caster) helps reduce the cost of an event by having cheaper meeting rooms, and especially cheaper hotel costs for participants.
There is a critical line in cost of participation that you cannot cross or your event will go bust, if you are catering to a middle class typical attendee. For a 3 day event, that line is $500 per person. For 4 full days that cost is $1000 per person. If you have hotel rooms at $150+ per night, then for a 3 day event, your participant budget is exceeded JUST from the hotel cost, let alone registration, meals, and travel. Shave the hotel cost to $75 per night, with the option of even cheaper rooms, and you are within the budget of the typcial trip for many folks. Travel time is of course the other major consideration, so you schedule for NEAR major centers of active participants (but not IN them).
That is why places like NYC (with hotel costs over $200 a night pretty much a “given”) are not viable options for events that are catering to the middle class. But sompleace like Lancaster (with an hour drive from BWI airport, and within 2-3 hour drive of 20 million people) are good choices for event locations.