Why do plastic drink bottles say "no refill"?

Some bottles are supposed to be returned to be refilled by the company that sterilizes them first. But those bottles also require a deposit that you get back on return, usually about 5 ¢.

When I was young almost all bottles were returnable and I begged my parents to let me walk to the store to return them so I could use the money for candy.

After I read some answers .... I must say that now I see how things get spread as fact when it's not true at all. The Idea that plastic water bottles break down and start to release plastic particles is not true at all....ah excuse me folks....with all due respect to you.... The Lexan and HDPE plastics (which are commonly used) are not biodegradable. It means they do not "break down"..their half life is a bout 10000 years. You breath more "out-gasses" from the normal air in your house everyday from your carpet, TV set, A/C or furnaces., etc. Let me point out that it is true that reused bottle do get nicked and marred so that it creates little places for bacteria to harbor and grow.....well gosh, let's be sensible, you wouldn't use a glass drinking glass over and over without washing it either would you? The real problem the environmentalist have with these bottles is the Dioxins they release when being burned, and rightly so I might add. That is really really bad for the environment! not to mention the trash laying around and the harm plastics do to animals in the wild. But honestly, Most of the negative things I read here about these bottles are urban legends. Yeah, it a marketing thing too.

I think it is because with the old glass bottles, you could turn them back in at the store and they would send them back to be cleaned and refilled. Like, did you ever get a six pack of Pepsi or Coke when you were little and it was the tall, glass bottles? And then you took them back to the store? Well, I think it says no refill on the plastic bottles because you can't sanitize them and recap them like you could the old glass bottles with the metal bottle caps. Make any sense?

No. it's just a law that they must put that on plastic bottles. Glass bottles are legal to refill, plastic is not.

The reason is that plastic breaks down and can leak toxicity into whatever beverage your drinking.

Glass will not.

Plastic is also a curse to our environment. try to avoid plastic if you can.

because you probably couldn't take it to the store and get it refilled

I think it's unhealthy somehow.