It's another datum but the same information is available in other forms (else the problem wouldn't exist). It's also possible that mechanism has degraded/failed, "original" parts were "special" (and replacements are missing some crucial characteristic), etc.
Doorbells *tend* to be designed so you can retrofit them with minimal impact. People would be discouraged if they had to change out a transformer: Where is *yours* located? Is it affixed to the *side* of a Jbox? Or, to the top cover of one? Is the Jbox on a wall -- or hanging from the ceiling? Is it in a dimly lit basement? Will you need to hire an electrician to open the box and remove the wire nut connections to install the new XFMR? Will the 18AWG solid bell wire *snap* when you try to remove it from the screw terminals? Will there be enough of a service loop for you to strip the remaining wire and reattach it? Will you WONDER if it matters whether the red wire goes on the "first" terminal or the "second"?
"Gee, why don't we buy this OTHER doorbell, instead...?"