When I run Bitcoin core to synchronize the blockchain without getting innvolved in any transaction, the
wallet.dat gets written to nevertheless.
I believe this is the case because the wallet keeps track of the best chain. (However, I am not sure if this is the only change that is written to the wallet.)
Now, I am wondering why the wallet needs to keep track of the best chain. My possibly faulty understaning is that there is a consensus about the best chain which can be deduced from the blockchain. Hence, no seperate storing of it should be necessary.