There are a number of compelling reasons why Ron Paul might want to drop his presidential campaign.
First off, Mitt Romney has pretty much won the GOP nomination. That means the single-digit chance Congressman Paul had of sitting in the White House has now fallen to a number perilously close to zero.
Second, the trail is long, and the days are hard. Food is bad and sleep is limited. It can be tough to find the time to get in a good walk in the morning and an afternoon bike ride, as Paul likes to do.