The FCC’s statements address this:

> Recipients of a robocall have the ability to either pick up the phone or not. But on most devices, recipients of a robotext see at least some of an unwanted message immediately

> …unlike robocalls, scam text messages are hard to ignore or hang-up on and are nearly always read by the recipient – often immediately. In addition, robotexts can promote links to phishing websites or websites that can install malware on a consumer’s phone.

And per the article this particular regulation is already in effect for calls:

> The FCC already requires similar blocking of voice calls from these types of numbers.