Thousands have left the country and done things like that, but your average Joe may have money, but not enough to live in another country until they die. The same as most people in this country could not do the same.
The camps are full, hence the overflow problem we have now. I mentioned this he other day, along with the stats. 26% of the Lebanese population is now made up of refugees. Every camp and spare bedroom is full. The UN does not have the means or money to build new ones.