If you don't use your countertops for either kli rishon or sheine, why do some require them to be kashered for Pesach?
Chicago Rabbinical Council’s Guidelines to Kashering Counter tops and Stovetops for Pesach and Countertops while explaining what countertops need to be kashered and how they can be kashered, also imply why they need to be kashered. Many materials are porous or can develop cracks. Other materials develop a film that needs to be cleaned (and will have been absorbed into the material over the course of the year) or hot foods can spill onto the countertops. Even if you are careful, it is possible that some time during the year, your countertop can come into contact with hot chametz (as explained in various sources and by my LOR).
As a result, it is best to treat the countertop in the same way as you treat your sink, especially in the areas near your stove top.