First off, all of the beaches in Texas are open to the public. This includes vehicular access. If nesting beaches aren't adequately protected, turtles would be at risk from cars and trucks driving up and down the beach. Cars can hit adult turtles, crush nests or hatchlings as they scuttle towards the water, or bury eggs too deeply in the sand. Hatchlings making their way to the sea can also be trapped in tire tracks.
Humans present other threats to the turtles, too.
For example, some people are still interested in eating turtle meat and eggs. Illegal poaching is obviously a big impediment to recovery. But even well-meaning actions can be harmful. Turtle hatchlings are awfully cute, and they might be very tempting to people who want to handle them or pick them up as they scurry across the beach. This period, however, when hatchlings dig themselves out of the sand and scamper across the beach into the surf is critical.