Termites are a good example.

They are a natural way to break down wood. And they can eat your house. Thus we have come up with ways to mitigate them. Now there is an entire industry around preventing termites, fixing termite damage, etc..

So, the problem is, we find some microbe that eats plastics. Boom, now we have a new problem, we need an entire industry to prevent them from eating the plastics we don't want them to eat. Think of traveling with your laptop, 'oops, got a little bit of plastic eating microbe, guess i'm buying a new laptop'