A new generation of street-food lovers is lining up at food trucks and food carts like never before. Little do they know that neither food trucks nor food carts are new to the streets of American cities. Like so many other popular trends, they are the latest version of a long-standing part of American and world culture. Food-industry observers claim that the food-truck business is increasing largely in response to the slow-growing economy. People are seeking inexpensive breakfasts and lunches. Also, employees today are often pressed for time, with more work and shorter lunch hours. These factors make the mobile-food concept more appealing than ever.