It's not about Dominicans...
It is a question of tourism. To understand, you have to look past national pride and think in terms of the campaign's goal: attracting foriegners to the island. Shakira will be much more effetive than Milly Quesada or any other Dominican, including Oscar de la Renta.
Please don't misunderstand, I know that Dominicans who don't live in the country bring considerable revenue to the island when they visit; but no effort is needed to attract them because they come in large numbers anyway, as anyone who travels on flights from New York knows. Shakira has become one of very few Latin entertainers with mainstream appeal. There is no such Dominican entertainer. There are many such athletes of course but they don't compete in sports that are well known outside the Americas. You probably know many Dominican Republic tourists come from Europe, where Sammy Sosa and Luis Polonia aren't exactly hot properties.
Dolores mentioned the opera star. Like him, Shakira has made some significant commercial and residential real estate investments in the eastern region. So, she has a vested interest in promoting the area.