In principle, shinkai (ranks granted to Shinto gods) were never reduced, and unlike humans whose lives come to an end, gods have unlimited life-spans, which led to many shrines becoming Shoichii with time.
神階は原則として格下げられることがなく、また、いつか寿命がくる人と違い、神には寿命がないので、年を経るごとに多くの神社が「正一位」となってしまった。