The airlines can, but they don't because if its not mandated they aren't likely to do it unless it is advantageous for them.
There is an additional data recorder that operates like this the "Quick Data Recorder" designed to be able to be removed and read regularly by the ground crew to better diagnose and fix the plane.
Unfortunately the voice recorders are really only used when the plane crashes, so the airlines aren't going to pay to put them in.
Add to this the fact that anything being hooked into critical plane systems (and a lot of them are considered critical) needs to go through hundreds of hours of testing means your not talking a cheap option.
There is an additional data recorder that operates like this the "Quick Data Recorder" designed to be able to be removed and read regularly by the ground crew to better diagnose and fix the plane.
Unfortunately the voice recorders are really only used when the plane crashes, so the airlines aren't going to pay to put them in.
Add to this the fact that anything being hooked into critical plane systems (and a lot of them are considered critical) needs to go through hundreds of hours of testing means your not talking a cheap option.