We haven't taken carseats for our girls any of the times we have traveled with them. When they were an infant I held them (under 1) = the next time we go the youngest will be a week away from her 3rd bday- she will have her own seat but we are not bringing a carseat for her, nor for our 6 and 8 yr old. I know some will think that is a bad decision but it is the one we have made for ourselves and our situation and it works for us. Now times we have left WDW and gone to SeaWorld there has always been a minivan taxi at our hotel that we have used that had carseats available if needed- had they looked supect I wouldn't have used them. Overall do you have to have one No but you may choose one for the reasons others have stated- personally it is just another thing I have to lug around with us and I choose not to.