On: 20% of requests for Wikimedia Commons are for one ...

[yreg]

No, it's not universally considered a theft. Wikimedia explicitly permits hotlinking[0]. So does xkcd, imgur and tons of other sites.

Of course when someone doesn't want us to hotlink to their assets then don't do it.

[0] https://commons.wikimedia.org/wiki/Commons:Reusing_content_o...