Its actually a good idea as the few grams of plastic required to manufacture a plastic bag and straw vs the PET or Glass bottle means the resultant environmental impact is far less.
Only South Australia has a funded recycling program for glass and PET which means the resuns on these are much higher for recycling - in the other States of Australia glass and PET bottles are littered all over the place.
We use PET bottles for home brew ... so it is recycled here.
Its is a good idea.
Street vendors in Thailand sell soup, iced tea and coffee and other drinks in plastic bags.
The West still has a lot to learn from others ... sadly.
Mind you things like kilts, haggis and frogs legs are not included.