(edit: removed the part in which I stated that burning bagasse is clean energy as I want the discussion to be focused on my first point)
This has changed, because it's now prevalent enough that I'd consider it "not unusual" to have my own cup. Also plenty of places now offer small discounts. I'm not doing it for the discounts, but that of course adds to the normalization. (Also: Covid makes things more complicated and I've been wary of using my reusable cup once again, though I also massively reduced my coffee-not-at-home-consumption, and after all that'll be over at some point.)
Coffee shops here in Ireland stopped accepting reusable cups during 2020.
I think it’s fairly unreasonable to expect people to lug around everything they might need for the day every day.
Soldiers and campers have had mess kits where they cooked and ate their food from a compact portable system for at least 100 years.
If anything, modern be silicone has increased the portability and utility of mess kits dramatically in the last 2 decades