Well, you don't know what tomorrow you will need. I remember my grandmother needing to make the house accessible after my grandfather lost control of half his body after a stroke.
And those accessibility enhancements are not a problem even if they're not directly needed anymore: no steps between rooms, big sliding doors, lot of space for the shower etc. Even able people can appreciate those.
Like: build a house on only one floor so no stairs => no need for elevators later on. But it requires more floor space.
not hiding the scrollbars on your website doesn't cost you thousands of dollars so I don't really see the equivalence
Is it not an extra step to intentionally hide the scroll bar? And thus, simply no extra work to just... not? Scrolls bars are a convenient feature for all users, nobody is judging the appearance of your website around how it looks with a scroll bar.
Art? Nah. (Maybe once.) Dead horse gimmick, now.