Lots of Dominicans have Visa or even residency in Spain, Italy, and the Netherlands. My Neighbour will be in England very soon, as she has been approved. Quite a few Dominicans that I know actually have Spanish citizenship. My wife's sister is currently living in her great grandfather's house in Andalusia.So why doesn't Colombians, Venezuelans or Peruvians need a Visa? I don't think that citizens from those countries have less interest in leaving their home country than Dominicans.
Those who have enough money to leave normally wants to stay in the DR, and those who don't, normally don't have enough money to pay for the trip. And I don't believe that it would make any difference, those who are determined to leave DR and live illegally somewhere else will find the way with or without Visa requirements, it only "hurts" the rest of us who has to take those additional costs and steps to be able to take our families abroad.