There is considerable demand for 3-day cruises out of Baltimore. People want a weekend cruise that is easy to fit into their schedule and is affordable. The quick trip is long enough to be fun but short enough to avoid boredom.
A three day cruise is often combined with other activities for a varied and fun vacation. It's a strategy that follows the "don't put all your eggs in one basket" saying. Watch a 3 day cruise video on YouTube.
Unfortunately, the Congress passed legislation that makes it impossible to offer a 3-day cruise from Baltimore. The large ships sailing from here were built in other countries and the law says that they must always visit a foreign port on their cruises. The sticking point is that there is no foreign port close enough to Maryland to do a cruise as short as just 3 days.