Why not? It's not as if they couldn't get off the corridor if a particular city or distribution point is their destination. It's the same with trucks.
The goal is to route them around metropolitan areas if the destination is somewhere else.
If the purpose of the rail lines is to provide passenger service, should they not go from city to city?
The closest TTC-35 will get to DFW is about 15 miles east. The closest to San Antonio will be about 20 miles southeast. And according to the map, the I-69 segment looks pretty far from Houston.
I agree we need highways to ease traffic... but this is a big monstrosity with commuter rail that is unnecessary.