Plastic bags and bottles should not be manufactured and use because:-
1. they pollute the environment. they do not get decomposed by natural methods. if we bury them for years also, then also decomposers can't break down it.
2. they are toxic for environment and produce harmful gas when burned.
3. they may block the pipes if allowed to went down the drain.
4. any animals who eats it by mistake may get choked and die.