DL, just like AA, UA, and almost every other carrier in the world must sometimes gate-check carry on luggage because there is not enough room in the overhead bins or the seat in front of you to fit everything. Even on widebodies this is sometimes the case. It has been this way for many years, so this is nothing new.

While it is less likely on a larger aircraft and more likely on smaller regional jets, you always need to be prepared, particularly if you are in one of the later boarding groups.