Why is targeting a specific group of customers usually more successful than trying to appeal to everyone?

Targeting a specific group of customers is usually more successful than trying to appeal to everyone since everyone has different wants. This is usually categorized by age since majority of wants can be influenced by our peers or people that normally communicate to each other. For example, a small and light weight laptop may appeal more towards young adults / late teens since it is suitable for their needs such as convenience for university.