Pageless mode is indeed a global setting. I turn on pageless mode on my document with wide tables and everyone sees scrollbars with the wide tables.

I use "view > text width" to change the text width to medium or wide. This is a personal setting. It looks better for me but is still miserable for everyone else.

Suppose I forget that I changed "view > text width" and some time later I go about creating more documents that require this setting. Now, I'm unintentionally creating content that is difficult for all others to read with no idea of the misery I'm spreading until someone complains.