When you call a company, any company, it costs them money. If a broker has 5000 accounts with CMKX shares in them, and each of these shareholders calls several times, the costs would be large not counting that the call volume would be well above normal thereby clogging the system and preventing normal business from being transacted.
The large brokerages may have decided that simply running a program to request certs for all CMKX shares in all accounts would be more cost effective for them. A $50 fee for issuing a cert (minus the $16.50 paid to the TA) only leaves $33.50 for the broker and call center costs for handling one phone call average around $14.50. It is easy to see that just a couple of calls on each account would put them in the red when handling that request not counting the money lost by not being able to service other calls.