How can I suppress the headers from CLI CURL's output of request

Simply remove the -i switch from your curl command.

man curl

said :

-i, --include
(HTTP) Include the HTTP-header in the output. The HTTP-header includes things like server-name, date of the document, HTTP-version and more...

In order to suppress output from CURL CLI --silent option can be used. It perfectly works when curl output is piped as well.

-s, --silent        Silent mode (don't output anything)