Amadeus has about 2500 developers ... this is not enough to keep up with the demand from the airlines. Yes - Amadeus is happy to have them, but they all have to wait in the queue for conversion.

The new Amadeus GDS has been built ground up rather than being a 1970s system that's been modified / tacked on to over the past 30 years. Its faster, more reliable, far more customisable and basically has all the features that airlines want. Amadeus also hosts all the data, whereas on many legacy systems the airlines are responsible for this themselves.