Does every wool suit or garment need to be checked for shatnez or can one rely on “Rove”, that the majority of suits and clothes do not contain shaatnez?
You are asking an interesting question. Even if most suits and clothes in the world are not shatnez, however we only say that it is botil b’rov if it isn’t something that is choshuv, and a suit is a davar choshuv and not botil. Secondly, something that can be easily verified is not automatically botil, because it isn’t considered a safek. Another reason is because the suit says the name of the company on it, and often it is known that this companies suits are problematic, which would make the suits kavuah, and not botil b’rov.
Conversation with R’ Elchonon Cohen Shlit”a, author of Hashatnez L’halacha U’lma’aseh.