Why Hepatitis B Core Antigen (HbcAg) is not detected in Serum?

During the lab diagnosis of  Hepatitis B, we perform serological tests. In which we can detect Antigens, HBsAg, HBeAg, Anti-HBs, Anti-HBc (Antibody against Hepatitis B core antigen). You might have wondered if there is antibody in the serum against Hepatitis B core antigen, why dont we can detect Hepatitis B core Antigen (HBcAg) from the serum.
 In this blog post i have collected some information so clarify about this issue.
Hepatitis B c Antigen (HBcAg) is an intracellular antigen synthesized within infected hepatocytes. Hepatitis B core antigen (HBcAg) are expressed by infected hepatocytes.
Hepatitis B Core Antigen production and Assembly source: http://depts.washington.edu
 Most of the HBcAg that is generated is assembled into the viral core (nucleocapsid).

Free HBcAg does not circulate in significant quantity in the blood, but it does circulate as part of the intact hepatitis B virion.
So HBcAg is not detected on serum tests but antibodies produced against HbcAg i.e. (anti-HBc) can be detected  in the serum throughout the course of HBV infection