With some headends using the legacy STARs; ironically, the lack of LFs should have been a violation against FCC standards.
While I agree with you in theory, I don't think there's actually any FCC regulation requiring
any cable network to display weather warnings. What the FCC
does require, however, is that the display of local weather warnings be accompanied by an audible tone. This is why the WeatherStar III had to be retired: it was capable of producing a tone (assuming it still worked on any given unit) only during the first display of a warning, but not on any subsequent warnings. An upgrade to conform to FCC regulations would have been too expensive and time-consuming for a 20-year-old computer system.
By its nature, the national feed local forecast/L-bar/LDL can only give so much information. Even when it shows weather advisories and warnings on a national map, they're not detailed enough to warrant the warning tone: a tone for a tornado warning in ABC county in Texas would be not only worthless, but actually "crying wolf" for a viewer in XYZ County in Montana watching the national feed forecast.
I do agree with you 100%, though, that the loss of non-Intellistar LDLs and the lack of non-Intellistar L-bars is a major drawback for TWC's viewership. Non-Intellistars are now able to broadcast anything (not counting weather advisories)
only during regular local forecast segments - and those are becoming fewer and fewer in number, apparently. While the Intellistar is used in a lot of headends, it's not used everywhere, leaving so many TWC viewers without their own local weather for large amounts of time. The "tune to Weatherscan instead" argument doesn't even work, considering how few people have it.