Good to see such support.
Afraid the answer is a lot more complex, but fundamentally it revolves around funding.
The emphasis is shifting to the universities carrying out the research, while the Met Office ( which has done this work since the 1940s ) is now becoming a more commercial operation.
The economics of operating the current aircraft have played a large part in the move to the new platform.
One would hope the expertise built up over the years by Snoopy's crew and support personnel is not lost when operations are transferred to the new aircraft.