I think you'll find that, like most things in aviation these days, it's all down to cost and the financial return the airport can make.
Look at it this way, the airport operator plans the new facility, say it costs £50m, the locos know that their charges will be based around funding this, so they say "take out the airbridges and save £2m" we don't want them and aren't going to pay for them. If you were the airport operator why would you borrow an extra £2m and pay interest on it, when you're not going to get any return ?
The airline only cares about an on time departure and swift turnaround, do really think any airline cares about its passengers once they have departed the aircraft on arrival ?