>It’s your data.
>As soon as you decide to upload it somewhere else, it's not.
That may be how everyone is treating it but that isn’t the only or even the obvious way for it to be. Mailing something doesn’t give the mailing service a right to open and scan the contents of your letter, even if it could do so without damaging anything. Parking your car with a valet service does not grant the service the right to drive your car to make deliveries while you’re not using it. Sending photo film to be developed doesn’t give the developing service a right to make their own copies of it. And so on.
It’s not unreasonable for a user to think of their emailing something as just granting the mail service the minimal privileges necessary to transmit and deliver the message to the explicitly intended recipient.
That may be how everyone is treating it but that isn’t the only or even the obvious way for it to be. Mailing something doesn’t give the mailing service a right to open and scan the contents of your letter, even if it could do so without damaging anything. Parking your car with a valet service does not grant the service the right to drive your car to make deliveries while you’re not using it. Sending photo film to be developed doesn’t give the developing service a right to make their own copies of it. And so on.
It’s not unreasonable for a user to think of their emailing something as just granting the mail service the minimal privileges necessary to transmit and deliver the message to the explicitly intended recipient.