Meanwhile, the right margin of page 3 looks has a "shadow" that goes all the way to the right because the left margin of page 2 pokes out underneath it - your eye might want to glide to the end of the block, but the sentence stops earlier.
It looks better when it's aligned, which is also why you can specify a left- and right margin that alternates on odd and even pages.
This is obviously only a concern for books and papers, and not so much for e.g. glossy magazines.
Typesetters are known to be very specific about small details. E. g. tables are typeset with meticulous alignment rules. It may look superfluous, but it is not. The nature of the craft is that it has to be invisible unless you know where to look.
After reading this article I thought "wow that's really impressive and I hate it".
For the same reasons you mention, and the words seem to "blend together" into a blob of text and losing my interest.
Still super impressive that people do this though.
IIRC, the somewhat random allocation of trailing silent "e"s in English spelling can partly be explained by typesetters trying to fill lines.
Totally agree with you BTW. I find justification ugly as sin.