Affiliation contracts are “take it or leave it” agreements where you have to accept or reject the contract as a whole.
Accession agreements are designed to simplify business transactions by standardizing the agreement between the supplier and the buyer.
In order to ensure enforceability, accession agreements cannot be unreasonably unilateral.
Ultimately, the courts decide what is reasonable in the framework of an adhesion contract. This changes over time and may differ between jurisdictions.