I guess everybody has their own preconceptions of what's wasteful.

I grew up in the era of 14.4k modems, so I'm used to thinking that network bandwidth is many, many orders of magnitude more scarce and valuable than CPU time.

To me, it's wasteful to download an entire image over the Internet if you can easily compute it on the client.

Think about all the systems you're activating along the way to download that image: routers, servers, even a disk somewhere far away (if it's not cached on the server)... All that just to avoid one pass of processing on data you already had in RAM on the client.