Are 2 revision shafts necessary?

Hello everyone, the installation of 2 inspection shafts is included in the offer from my general contractor and I am wondering when something like that would be necessary?

Are there any advantages? It wouldn’t be cheap at all, so I would also like to do without it if there is no necessity (especially with soil class 5-6).

PS. I will of course discuss this at the next appointment with the general contractor, but I would like to have second opinions in advance.

In case of a blockage, you can flush yourself very quickly without having to call a professional. For this reason, we have 2 inspection shafts and one transfer shaft. I would definitely provide at least one shaft. Otherwise, what does he say about why he definitely wants to make two and at which positions? Asking usually costs nothing, and the answer is often coherent and understandable.

Thank you for the answer! I already understand why it can even make sense.

I have an appointment with the [GU] in almost 2 weeks and will clarify it with him. I was just wondering why something like that is done in the first place.