It's important to note that this change impacts only the kind of forwarding, where the sender doesn't change.

That's different than pressing the "forward" button in your email client, where the email is not being forwarded from your intermediary mailbox.

In the first case, you're practically impersonating the original sender, which you're typically not authorized to do so. This is also what scammers do to trick people into believing a higher authority authorized a payment to a malicious entity.

In the latter you're just sending an email that contains the original email. The difference here is that the recipient doesn't see the original sender immediately, but has to look in the attached email, or into the email history to find this out.

So, to answer your question, this change is being made to make it harder for scammers to scam people.