Erich Roucka was researching the increasing degree of acidity in the body as people age, and he is a reference in this field, walked himself the bicarbonate path and took the powder for 40 years and I don't think he ever reached a balanced pH.
Bicarbonate is produced naturally by the body. My guess is that like in the case of hormones, etc., if you give the body something that it naturally produces the body will reduce its natural production of it.