why is not there a sloth emoji?

I agree. I think it would be a great emoji to use when someone is not texting back fast enough too! Apple does not actually make the emojis themselves, nor do they take requests. Apple uses Unicode emojis and then transforms them to the signature Apple style. You should submit an emoji request to https://www.emojirequest.com/

You can send feedback to Apple > http://www.apple.com/feedback/iphone.html

Hi

Proposals for new Emoji characters should be submitted to Unicode, not to Apple:

http://unicode.org/emoji/selection.html