> Why not just include the contract in the email then?
One of the advantages of a fixed reference document is that, apart from confirming that you have that document, you don't have to read it to know what it says — and to have a sufficient degree of comfort that the other side isn't trying to sneak something past you.
In contrast, if Party A (or its lawyer) copies and pastes the contents of a reference document into an email, then Party B will have to read the thing, which will take time and, if a lawyer is involved, cost money in legal fees.
An analog that comes to mind is the INCOTERMS rules for shipping goods: If you agree that the goods will be shipped DDP (Delivered Duty Paid), or EXW (Ex Works), or whatever, then you know what you're getting, without having to read the rule again to be sure the other party isn't trying to slip something in on you.
Another analogy is arbitration: If you agree to the American Arbitration Association's rules for commercial arbitration, then all concerned can go to the AAA Website to get a reference copy.
I see your point here, but I'd counter that it's technologically trivial to check that the text matches a reference. If you already have a copy of the contract that you've read and agreed to, and this email claims to have included the same contract in a standard form, then nobody needs to sit down and read the thing.
> it's technologically trivial to check that the text [of an email] matches a reference
Remember who we're talking about here: Lawyers and business people — too many of whom don't even know how to use Microsoft Word "properly." [0]
(You have no idea how many contract drafts I review in Word where the drafter used 'Normal' style for everything and just bold-faced the headings; used blank lines to put spacing between paragraphs; and didn't know how to do automatic paragraph numbering.)
One of the advantages of a fixed reference document is that, apart from confirming that you have that document, you don't have to read it to know what it says — and to have a sufficient degree of comfort that the other side isn't trying to sneak something past you.
In contrast, if Party A (or its lawyer) copies and pastes the contents of a reference document into an email, then Party B will have to read the thing, which will take time and, if a lawyer is involved, cost money in legal fees.
An analog that comes to mind is the INCOTERMS rules for shipping goods: If you agree that the goods will be shipped DDP (Delivered Duty Paid), or EXW (Ex Works), or whatever, then you know what you're getting, without having to read the rule again to be sure the other party isn't trying to slip something in on you.
Another analogy is arbitration: If you agree to the American Arbitration Association's rules for commercial arbitration, then all concerned can go to the AAA Website to get a reference copy.