What is the reason for using an http url with the https_proxy?

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When using an HTTPS proxy, the HTTPS traffic is encrypted and then sent to the proxy server. However, if the URL starts with "http", it means it is not using HTTPS encryption and is sent in clear text. The reason for using an HTTP URL with an HTTPS proxy is to allow traffic that is not encrypted to also be directed through the proxy server. This can be useful in certain situations where encryption is not necessary or where certain websites/applications do not support HTTPS.