HTTPS is a Google ranking signal, one of ~200, though it doesn't make any sense whatsoever to use HTTPS technology on a site that doesn't process payments or/and hold other sensitive information.
But Google is so obviously on a mission to make all websites switch to HTTPS, regardless of whether they process sensitive information or not. Hence the red warning when a site doesn't use HTTPS.
We can reasonably expect the penalty to non-HTTPS sites to only get bigger.
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