Automated processes, quick snapshots that were taken under insufficient control, pictures taken from moving platforms or of moving objects... Maybe the picture was intentionally taken with other things in focus than the ones you are interested in now.

Honestly, how your comment came to be escapes me. Can you seriously not see the utility in those approaches? Do you really think blurry pictures are "not a thing anymore"?

99% of the public using their crappy mobile phone cameras.

Surveillance cameras.

telescopes?