* when you buy bitcoin cheap you earn, while others buy bitcoin which is expensive they lose.
* The rich people could earn more in investing bitcoin while poor people could lose more. (vice versa the rich people may lose more and poor people can earn more)
Well, bitcoin as investment has this disadvantage that might happen in some cases.
But keep in mind bitcoin is a currency, so people will use it to sell their goods/services and receive bitcoin as payment. It can only benefit both sides of the transaction, being them rich or poor.
* the use of bitcoin to travel spending outside in the country is more like selling your country asset and that could destroy the economy of that certain country.
That is not true. Everyone who invests in bitcoin is willing to make profit from that and once they achieve this profit the country where the investor lives will be the mainly benefited as the investor is probably going to spend his money (profit from bitcoin) where he lives. So he is going to boost the local services sector for sure.