Some people don't make plans because they like to be spontaneous. They enjoy the excitement of not knowing what will happen next and prefer to go with the flow instead of being tied down by plans.
Some people feel unsure about the future, so they don't like to make plans. They might have busy schedules that change a lot, making it hard to stick to plans.
Some people are just more laid-back and don't like to plan. They are flexible and like to adjust to situations as they come, instead of making detailed plans.