This is a random question I have been wondering for a while now. Not to long ago when I learned the Kanji 下, I was taught that it is used in the word ください, but as I have seen a few random Japanese words around (mostly on odd stuff like CDs or those baby changing stations in restrooms) don’t use the Kanji. I usually just see ください　instead of 下さい. Is there any specific reason to this or is it fairly interchangeable? I know for some words the Kana is preferred due to complexity of the Kanji but in this case it is easier to use the Kanji.

It’s not to important of a question but if someone could answer it that would be pretty cool.

ありがとうごじます！