Don't have any way of knowing this for sure, but I believe the near collapse of the space shuttle program is the reason.
I thought that Hubble was kept in its orbit by small gas jets, and a gyro, maybe nuc powered. Perhaps it needs some more fuel??
And I thought that a revised shuttle is due to take off very soon, even with a female commander! Hubble should be its first mission
Even before the loss of the shuttle NASA was having conferences on the termination of Hubble. One speaker described it as being like putting your faithful old dog to sleep, heartbreaking but something that had to be faced.
We are dealing with what the Russians had to face when they sent MIR down to its destruction.