For many reasons, most if not all which have already been stated:
You have no idea if the baby will be late or have some unusual problems. You don't know if labor will have complications. Even if you plan to breast feed that may not work out so you are dealing with bottles and sterilization, etc. Some infants seem to sleep all of the time, but many (mine included) do NOT and trying to keep them happy when you are away from home can be tricky. With tiny ones, even short trips seem to involve about as much planning as the Normandy invasion! It just seems like it would be much more hassle and stress than fun.
Being a new parent is harder than you can imagine. (Best job I ever had, but don't kid yourself -- being a conscientious, careful parent is incredibly difficult). Infants that age more often than not have crying jags, so what will you do if it is the middle of the night and the baby screams for hours. It will be extremely hot and humid and an infant will be miserable out in that heat -- I don't care if your stroller has an awning -- 90 temps and 90% humidity don't change with a little shade.
I am a big believer that infants that young really need quiet, calm secure environment. In a few months it might work out fine, but with a very young infant "vacationing" in an extremely hot area, with little space and privacy, is just asking for problems. When your child is six-weeks-old, I think that you would be thrilled just to be quietly at home and getting a long nap!