Saying that only critical applications need HTTPS is like saying that only those e-mails containing actual secrets need to remain private.
Privacy on the Internet is a bigger picture. If most of the websites you're visiting use HTTPS, it will be significantly more difficult for an eavesdropper to synthesize a profile of you and your habits. Also, the fact that you don't consider a particular website security-relevant might not apply to someone else. Someone in an oppressive regime might be at risk just for researching a particular news topic and will benefit from any news blog that serves its content over TLS.
Privacy aside, every download over HTTP gives a man-in-the-middle the opportunity to inject their own malicious content. A seemingly harmless download of a Word or PDF document could be silently replaced by malware. Then it won't matter that you downloaded it from a small site that seemed too unimportant to use HTTPS.
Especially with free certificate providers like Let's Encrypt, rolling out HTTPS even on small websites should be a no-brainer. You're contributing to a safer Internet where encryption hopefully soon becomes the norm.