The reason behind this is that the paper cups currently used by starbucks are rarely recycled -- technically, it can be achieved. However, as the film inside the existing paper cups is difficult to be separated from the paper cups themselves, if it takes time to separate them and recycle the paper cups separately, the cost is much higher than that of directly manufacturing new ones.
In June, McDonald's tested plastic-free packaging on a small German market: waffle cups for wheaten ice cream, wooden spoons for plastic scoops, and paper straws for plastic straws. The test has also sparked complaints from some customers: McDonald's straws are also prone to softening, and some don't like the taste of wooden spoons. This is also one of the environmental dilemmas faced by many catering companies at present -- paper appliances have a poor sense of experience, while plastic products are not environmentally friendly. Under the current technological constraints, it will take time to find a solution to both problems.