The simplest reason is that it doesn't necessarily lead to cutting back on plastic production and could even be used as an excuse to boost production of petroleum based plastics instead of plant based plastics.

Secondary is that with the glut of information and social media easily available to the public, there are legions of "experts" on topics where their only qualification is they read an opinion piece on a Facebook post. The heavy criticism of nuclear energy while ignoring "where do they get the rare metals?" for renewables is a good example. There is no quick fix to the problems currently facing humanity and sadly there will be those who cannot recognize the intermediate steps we must take to ween ourselves off our destructive habits.