Thanks for Question. I am a mango cultivator so I will try to answer your question.

It's just 2 years since I have started harvesting. I also wanted to allow mango to ripe on tree naturally. And you know that it's always possible and mangoes tasted best when they ripe on trees.

But I faced some problems:

1. You need 24X7 care taker
2. Once they started ripening on tree they attract Parrots who come in group of hundreds. My pea crop was completely destroyed by these beautiful birds.?
3. And if you are unfortunate enough then monkeys will get to know that mangoes on trees are ready to eat ?. They attacked my field some days back and we had tough time.
4. Marketing: Generally fields are far from city. If farmer will carry ripened mango then many will damage. Also it's not necessary that they will be bought and consumed in a day.

Hope I gave you the answer.