Killing off this gateway cuts off an avenue of escape that people might use to avoid TCR.
If you haven't heard of TCR, you should check it out because it is negatively impacting you somewhere.
Overseen by TMobile, The Campaign Registry is a pay-to-play scheme that applies to everyone who wants to send SMS to a ATT/TM/Vz user.
To onboard with TCR, applicants have to:
1) pay up front and pay more and then pay forever
2) jump thru needlessly complicated hoops (that become ever-moving goalposts for small biz and end users).
3) wait weeks->months then GOTO 2 again. And again.
The end result is more and more biz, MNVOs, orgs, etc are abandoning SMS. Trying to comply with TCR is too big a resource-sink for them.