You certainly have the freedom to conduct business independently with an insurer. However, after a car accident has injured you, the pain and worry caused by the event might make you vulnerable. In your haste to settle a claim, you could short change yourself if your injuries worsen in the days or weeks after you accept a settlement. Many car accident injuries, especially those to the neck or back, are notorious for late-blooming symptoms. For example, an injury that might have felt like a minor whiplash the first week starts to cause dizziness, headaches or numbness in the subsequent weeks. Ongoing symptoms like that might require additional medical care and time off of work.
Additionally, insurance companies are in the business of collecting premiums first and foremost and limiting what they pay in claims. An insurance adjuster will likely ask you questions about your injuries and how you feel. Any information that you provide will be recorded and potentially used against you in an attempt to devalue your claim. Asking a lawyer to handle conversations with an insurer spares you from technical conversations that might be hard to follow when you are in pain.