It is the competitive nature of certain pastimes that raises the question as to whether they are sports or hobbies. A sport could be defined as a competitive activity that can be performed by an individual or team that is played against others for entertainment purposes. The activity typically involves both physical exertion and skill.
Meanwhile hobbies are understood to be activities done alone or with others in one’s spare time for personal enjoyment. While certain hobbies can be done competitively, practically all sports function on a timetable laid down by an organization responsible for governing all related competitions.
Compare that to competitive hobbies that are done in one’s selected free time.