I have to comment as this is a bit of a former pet-peeve of mine. After 11 years here and in the DR , I have to say I have stopped letting it bother me. I see it like eposters here say as well, no thank you's at an appropriate time when for us its normal , like after a purchase at a tienda or when I relinquish right of away to a motorist, never wave of thank you. BUT on the other hand as some have pointed out, for exampole I had a minor surgery last month and almost everyone knew and most came to visit to wish me well, even many that don't visit so often. I love how Dominicans greet the whole room and never pass on the street without saying a genuine hello or ask about the family. When you walk own a tourist beach for example the Dominican's will almost always say Hola or Buen dia but most tourists and foreigners walk past staring at the sand.
Living here in Gaspar Hernandez for all of these years , I see Dominicans greeting each other and having a moment all over town, every day. The town is always bustling and everyone is always waving and smiling and taking that moment to interact. I don't consider it a lack of manners, I consider it all a cultural difference. Like they probably find it rude that we don't greet the room or say a welcoming hello to strangers as we pass or stop for a moment to ask about their family. My Dominican wife is one of the most gentle and kind people I have every known and though she tries to remember , its not a reflex for her, its more of a compliance to my requests to say please and thank you.........usually she remembers. I have tried to make her speak to our children using manners, and promised her better results , but they love her either way. And by the way, my kids seem to have adapted to both, as kids do, displaying a different mannerism when i am in the room ! LOL.