Encryption Is Not Convenient
Much of the time, telco encryption is deliberately weakened (set the 16 leading bits of the key to 0), so that officially interested parties can freely access users and conversations they wish to monitor. It is so much more convenient that way, no warrants, no oversight.
Right from the outset, the MNOs did not wish to know about SMS, they didn't notice, in any material sense of that word, its capability when GSM was introduced, but they did shut down the (ISDN compliant) dual SIM capability (because customers use it to save costs). MNOs had to be brow-beaten into accepting that users would make use of it, especially when roaming. Believe it or not, they took the same approach to data, remaining in denial about customer take-up until too late.
There are a number of organisations which have official and court approved access to telco switches. However, the number of staff who have access to the data centres which process the telco back-end systems is huge. A number are outsourced. I know of one that outsources its data centre processing to a company that has been bought by its principal competitor. They remain quite relaxed about this, despite ample evidence that there is much to be concerned about.
MNOs should not be allowed out.
Biting the hand that feeds IT
