The default status when you operate a business without forming any legal entity — you and the business are legally the same person.
A sole proprietorship is what you are by default if you're running a business without forming an LLC, corporation, or other legal entity. There's no formation required, no separate tax return, and minimal paperwork. The business and you are legally identical.
The problem is that this legal identity means unlimited personal liability. If a client sues your business, they're suing you personally. If your business can't pay a vendor, that vendor can come after your personal assets. There's no separation. This is why most serious businesses form an LLC or corporation relatively quickly: the liability protection alone is worth the filing fee.
Sole proprietorships do make sense in limited situations: very early testing of a business idea before you have customers or contracts, freelancing on the side while you explore viability, or extremely low-risk activities where liability exposure is minimal. But as soon as you start signing contracts, hiring people, or serving real customers, forming an entity is one of the most important protective steps you can take.