Hello Dirk,
Strange argumentation:
As an interested party (sic!) you spend €1000 on a soil survey to find out that you might not purchase the property after all. You do this for 5 properties and each further interested party does it on their own, instead of the seller having it done once and then passing the cost on to the actual buyer through the purchase price?
I can explain that to you ....
It is due to the peculiar mentality of people. The seller sees himself exposed to negotiations over the property price, often also to the alleged absurdity of pre-sale actions (e.g. soil surveys) on his part. So he tries to avoid these discussions as much as possible or reduce them to a minimum.
Moreover, it is the case that every provider who includes soil surveys in their scope of services has different requirements for the survey; often they do not even credit the actual amount when a builder brings the property + survey with them.
In this respect, it has become customary that everyone is the smith of their own fortune. Meaning, with regard to the question of the original poster: he buys a property, nothing more and nothing less. It is up to him to arrange everything else.
Rhenish regards