It's complicated. Essentially, YT spends 24 hours a day trying to dodge the fallout of stupid decisions taken during the previous 24 hours, ad infinitum. They were bashed for certain decisions related to 4k video (which used to be called 4k, then changed to 2160p, then back to 4k, then back to 2160p), leading to the current name scheme.

That's hilarious

4k and high bitrate 1080p are actually the same thing.

For starters, cull the immense amount of duplicated content. Look for some random common word and sort by recent, you'll see thousands of channels from India, Pakistan and similar nations reposting the exact same videos. There's also an ungodly amount of spam. These two things alone would, I'd guess, cut down a good chunk of server costs. Another thing is optimizing bitrate, I often get served "1080p" content featuring little more than a static image while browsing in my 6" phone.

Julius Caesar's memoir of war in Gaul makes use of VIIII, for instance. You're right that it's much rarer, but was still used contemporarily and in modern times.

Bushido is Japanese, this joke doesn't work.

Because it’s not like a wave, such as waves in the sea.

Actually, it is. It's the same meaning we've had for waves in physics since the first time someone figured how to plot a 2d graph. Only the medium is a quantum field instead of water, its amplitude is probabilistic instead of height, and instead of time we have some other property of distributions, usually space-time.