Puerto Rico - La Isla del Encanto

I just returned from a week in Puerto Rico where I attended the National Association of Hispanic Journalists annual convention.
While the island boasts a natural beauty, it's the people who make this island such a paradise. Everywhere I went, the people were so friendly and willing to talk to you.
At Spicy Caribbe, located at 154 Cristo St. in Old San Juan, I bought some incredible sauces - including banana ketchup. The shop sells various sauces, teas and other items. I struck up a conversation with the lady working, I believe she was the owner.
Being a self-proclaimed travel geek, I had my list of restaurants to try. All of which were recommended by fellow travelers. This nice lady looked at my list and added a few of her own, including El Jibarito, a small mom-and-pop restaurant I never would have found on my own. I headed there for lunch and was not disappointed.
Later in the afternoon as I headed toward El Moro from Fort Colon, an older gentleman showing great concern for my well-being, stopped on the sidewalk and said, "Mi'ja, slow down. Despacio." He noticed I was overheating from the afternoon sun. We talked for a bit, and each headed our own way.
Puerto Ricans are by far the friendliest people I have encountered.
But there is one thing that bothers me.
Puerto Rico is a U.S. territory and Puerto Ricans are U.S. citizens, but they are not afforded the full rights of U.S. citizens. I learned this while there.
Puerot Ricans can serve in the military and give their lives for the United States. They can vote in the primary election for President. But, and this is what I find so wrong and frankly undemocratic, they cannot vote in the presidential election.
I don't get it.
I know the debate has raged for a while over whether Puerto Rico should become the 51st state or be given its freedom to become its own country. And that's not for me to decide. That is something the Puerto Rican people must decide for themselves.
But what I can opine about is the injustice of not allowing them to vote for President. What they are being told is basically, you're good enough to fight for the United States and maybe even give your life for this country, but you're not good enough to help elect the President.
How is that democratic? What is worse is that so few Americans understand the politics that govern Puerto Rico. I'm still amazed at how many people think you need a passport to travel there and have no clue it is a U.S. territory.
I don't understand the logic behind allowing Puerto Ricans to vote in the primary but not in the general election. Who came up with this misguided logic?
Until Puerto Ricans decide their own fate, they should at least be given the right to vote in presidential elections