Getting a certified copy of a birth certificate requires proof of identity. If you don't have a government issued photo ID states typically require multiple forms of secondary documentation (some of which themselves require photo ID to obtain). The secondary documentation can be expensive to obtain (fees for the documents themselves plus the effort to locate the documents).

The secondary documentation that can be easily and cheaply obtained without a photo ID, such as a copy of a utility bill, can fail because of name match problems--if your birth certificate is for "Bartholomew Jo-Jo Simpson" and your electricity bill is for "Bart Simpson" that might not be accepted.