I suppose “harm” can be subjective in this context, and there are already some good replies here.
One more thing to add to the list that I’d consider harmful in creating a Gmail account is all of the privacy issues that come with having a Gmail account.
Out of respect for my recipients and myself, I wouldn’t want all of our emails being read.
We can go down the rabbit hole of “Email is inherently insecure anyways,” but that’s a separate discussion.