Can’t I resolve my tax debt myself?

Of course. But it’s a terrible idea in most cases. Just as you can represent yourself in court (i.e. Pro Se), it’s never a good idea to fight the IRS alone. It’s like going into a boxing match with your hands tied behind your back. Resolving tax debt involves a lot of evidentiary building and presenting a strong case. Consequently, the skill set of an attorney experienced in handling tax collection cases is likely to procure better results.