Because freelancing enables you to sell your skills anywhere! It doesn't matter who you are - you have skills! There's attributes about you maybe someone writing a book on wants to questions you about. There's hobbies you have that others want to explore or improve on. There's knowledge about certain subjects you know that other inquiring minds don't yet.
You should consider freelancing because you can make money through your computer, traveling, or from your home on the couch. It enables you to sell yourself while choosing your own hours and at your own price. Whether you're a musician, artist, videogamer, writer, videographer, geeky about one subject, have successful businesses or just like to read people's palms and teach magic tricks. You can freelance these things on platforms like Fiverr. You can pretty much sell any skill or service on Fiverr the freelancing platform.
Freelancing is a great bridge between working for others and working for yourself. Entrepreneurship is very hard and full of risks. Instead of having to commit your full schedule to a new business being built from scratch (20% fail their first year and 50% by 5 years) you can be a freelancer. If it pays off for you, then you get to transition into a newer better line of work without all the risks.