I think it just comes down to health of the battery and usage. Parasitic power draw should be consistent, I don't believe multiple cars are all suffering from an issue.
One thing I did find on my OEM battery was that dirt easily collected on the top of the battery, and within a groove running along the top, which combined with water spillage when filling up the washer reservoir. This created a circuit between +ve and -ve which increases the parasitic draw.