The enforcement mechanism relies on the receiving party (Twitter in this case) suing the fraudulent DMCA sender. This is troublesome, as these platforms have very little motivation to do anything beyond discarding fraudulent DMCA notices, and users of the platform that are the target of the DMCA notice might not have standing to take this matter into their own hands (IANAL).
Establishing certain mass-DMCA senders as often fraudulent would be risky to do without at least a summary judgment, so YouTube, Google, Twitter and ilk provide no pushback against repeat DMCA notice fraudsters as any perceived pushback could land them in court.