I know, they mean well. For a student who does not want to read the whole novel and still needs to know what this is all about, that might be a good idea. But I doubt that is the reason why the publisher puts these notes in the book.
They might even think, it's a classic, everyone knows the story already. Not really, there are always new generations, there are people who didn't have to read this particular book in school because the teacher chose another one, there are people who prefer to read the books instead of watching the many film adaptations available nowadays.
How often does the writer of the foreword tell you what happens in the story? A major event that you really don't want to know beforehand. Someone gets killed, a huge accident, a fire, a couple breaks up, you name it, they will have named it before you. It's almost as if someone read it for you and you don't even have to bother anymore.
Giving away too much, especially an essential point of the plot, definitely does not have the same effect on you, either. It dampens down the enjoyment of the read.
I asked my friends about this, they all agreed. Most of them skip it if they read the book for the first time, some read it afterwards. Some like to read it beforehand because they like the explanations in the introduction but even they agree that too much is given away.
The same argument goes for the reviews. It's better to read them afterwards, build your own opinion before you hear others agreeing or disagreeing with you.
Morale of the story. Don't read the introduction if you want to enjoy the novel.