DD and testing takes time. I work in a private, small regional company of 30 people. We rely on a free software for a certain service that we provide and were all very excited when we found out a newer version is available but it took us 2 years to start using the newer version across the board (which is still free).
We first used it with one project despite having 3 on the go and the new version is superior in every way. It takes time to train, test and gain feedback from those who use the software internally. If there are potential customers that have been interested for a while but couldn't take the finished product and test it, then there is still the evaluation period.
I don't know anything about how the music industry works but business is business. The big labels have to make sure they got their bases covered and their bottom line is not affected before they sign a deal that changes how they do business.