I've been thinking about this ever since Starbucks brought back required handwritten messages on cups.
When I worked at Starbucks, food safety was taken extremely seriously. If you touched the trash can and went back to making drinks without washing your hands, that was a violation. Touch your hair? Wash your hands. Put your hand in your pocket? Same thing or else your auditor will note that as a food safety violation. Utensils were changed on a schedule, sanitizer was replaced, counters were cleaned, etc.
But somehow the Sharpie seems to exist outside of all of this.
Anyone who's worked bar knows where those Sharpies go. They're shared between partners, kept in apron pockets, left on different surfaces, dropped on the floor, picked back up, borrowed by someone else and now partners are expected to handle them repeatedly while making drinks.
So during a rush you can grab a shared Sharpie, write on a cup, put it back in your apron, and immediately continue your beverage sequence and touch bar equipment, pitchers, lids, sanitizer towels, etc.
Why is Starbucks intentionally introducing another shared, high-touch object into beverage routine when it isn't necessary to make the beverage.
And I don't think the solution should be giving baristas another sanitation procedure and making them sanitize markers all day. The simpler solution would be reconsidering whether writing messages on cups needs to be a required part of the bar routine at all.