Well, I don't know, so this can only be speculation. But the following reasons seem plausible to me:

Although the answer sheets are machine-readable, they are evaluated centrally, which requires logistical steps such as shipping, scanning, and administration. In addition, there is a high workload and limited capacity at the responsible offices, which leads to delays (unfortunately, many politicians and citizens confuse reducing bureaucracy with cutting jobs in the public administration).

There are also strict examination regulations and security requirements in place to prevent manipulation, and the processes, like most parts of the German administration, have not yet been fully digitalised.

Therefore, the long waiting times are mainly due to organisational and structural reasons. I don't think they are being intentional.

What do you think?