drafting a QB at 4 with the intent of sitting him behind Romo for multiple years is incredibly unconventional for an NFL team. Even the Colts just decided to move on from Peyton Manning and go full rebuild when they drafted Luck. If you have a QB you intend on moving forward with for the next few seasons there is no logical reason to select a QB top 5 as an insurance policy. It simply does not happen, and for good reason, that's way too much of an investment for what you are hoping for is zero return the first few years.
The team is still in a win now mode with Romo as the QB, you draft a QB with a top 5 pick then it sends a message that as a FO you have no clear vision or plan for the time being. If you're not committed to your QB and exhausting your resources to help him win then just move on and let Tony try to win elsewhere. Otherwise you're just in a purgatory state waiting for him to retire while the next guy gets ready, and that simply isn't how the NFL works.