It's not even only interviewers. I get at least one proactive job application per week at my small 2-people company. I'm not sure why these people do it, but most of them seem to have spent effort researching my company, so they mention relevant skills. But I'm not planning to hire anyone and I haven't had a job opening posted in years, so in a way it's just manually-written spam to me. In the beginning I still replied to the emails but a few of them started being argumentative or tried to call me, so now I just delete em without reply.