These were discussed recently on the RV forum. One guy said he replied to a spam text "Does this ever work?" He actually got a reply of "Sometimes".
I've heard the same. I know two women who have fallen for these scams, both intelligent, educated, one with a doctorate. One was an IRS scam that said to buy $1500 worth of iTunes cards and to text pictures of the numbers. The other was a long lost "cousin" stuck in jail out of the country.
The phone companies absolutely could put a stop to them, but it would lose them money in burner accounts.