Forest park is about ten square miles, and maybe a third is overrun by ivy. That's solvable by a sufficiently large human work crew, but it wouldn't be easy.
Developing, manufacturing, and operating a crew of robots just for this one particular ivy problem wouldn't be worth the cost, but invasive species are a widespread problem and are sometimes on much larger scales, like hundreds or thousands of square miles. At some point, using people isn't a realistic option. If we can solve larger invasive species problems for less money than a human work crew, then that seems like a win.
Developing, manufacturing, and operating a crew of robots just for this one particular ivy problem wouldn't be worth the cost, but invasive species are a widespread problem and are sometimes on much larger scales, like hundreds or thousands of square miles. At some point, using people isn't a realistic option. If we can solve larger invasive species problems for less money than a human work crew, then that seems like a win.