While the spacing of items on any given view is nice on a big screen, it's terrible on a laptop. Anyone trying to do work on a laptop screen can only view a few columns and a handful of rows at a time because there is so much whitespace at the top of the page and on the sides where icons and row numbers are. Currently, on a 10" screen, which is standard at my company, the page and view headers take up a third of the space and I can only fit 7-8 columns, including the column for attachments/etc., at a time, which is nothing when you are customizing your smartsheets with helper columns and calculation columns.
While most users won't have a need to maximize their workable screen space, advanced and power users might. Having a compact view option in individual settings or at the top of the page that people could toggle between would allow people the option to have the comfortable normal view on a big screen AND a space-saving view when on small screens, or to just choose which they prefer in general.