Constitutional protections exist for very good reasons.  If one wants to forgo exercising the right to remain silent and the right to have an attorney present, or if one prefers to sign statements or admissions of guilt without review by an attorney, then well and good.  Doing so, however, is regarded as patently foolish even by police officers and prosecutors themselves.  It's about as foolish as walking into a car dealership and demanding to pay the full sticker price.