I don’t want to get too political in this but a lot of it is because of political reasons. Outside of the main capitals per provinces, the country is technically still a 3rd world country and is a communist nation. Many of these resorts and attractions are funded by China and Russia oligarchs, while employing poor Vietnamese citizens. These oligarchs then take in the money from tourism. You’ll be shock at how many Chinese and Russian directions you see at these resorts and attractions. They don’t care about preserving the environment when the country isn’t theirs. Of course, the Vietnamese communism goes along with this because they also get their shares with business booming.