Why are there no chlorate esters? Or are they just undocumented or too unstable? I've seen perchlorate esters, but google "chlorate esters" and only perchlorate esters come up.
Your initial statement is wrong. There are organic chlorates. When you want to search compounds, try chemical search engine like PubChem or ChemSpider instead of google. Even google lead you to something if you read carefully. It is no reason that chlorate ester can not exist and they do exist. Below is the link to the PubChem entry of Choric Acid, Methyl Ester, which is Methyl Chlorate.