It's because they are not capable of original writing anymore. Sure this gimmick can work once in a while a few months or issues at a time every 10-20 years. But they are overplaying it.
You can add in Eddie March and Whoever the Guardsman guy was. From the under 100's. Maybe even the teenage daughter of Yinsen and more I am sure. There was also the LMD in the pre-issue 20's I think...so they have done the rogue AI thing taking his place a few times as well. Yeah...just done with it.
Didn't list Eddie March, happy Hogan or Michael and Kevin obrien as they were one offs.
But yeah, the on has been replaced too often.
Now he is allegedly a replicant of the real Tony...ugh