I can see straws no longer being allowed on cruises. Straws, and other plastic items, are causing significant problems for the ocean wildlife. Animals are dying from plastic straws. So there is a on-going and increasing push to reduce/eliminate the use of plastic drinking straws.
I woudn’t bring your own unless you are talking about a REUSABLE drink cup with reusable straw rather than disposable.
We use our own reusable cups all the time. Mostly insulated stainless steel ones. Don’t think I want to pack those for our flights and cruise, but a lighter weight option.
I’m just worried about no lids or straws for my kids mostly. We’d bring reusable cups mostly for them.