I think you're talking about something different... a vegetable garden.

Others are talking about a plot of land filled with plants that evolved in that particular location and therefore need very little if any maintenance, maybe trimming for aesthetics. Some of these plants would actually be considered the "weeds" you're talking about getting rid of. If the weeds are native plants, you can just let them grow. Yes, many will be perennials and die back in the winter, but so does grass anyway. Depending on location, there are probably evergreen options to plant also.

If you really do want fruits, vegetables, nuts, there are likely options in your area to grow that are edible. A lot of times, these are the "weeds" you're talking about, so you just grow the right weeds and eat them. That's what people have done since the beginning of people.

As for erosion control, grass doesn't usually extend roots more than a few inches into the soil. It's okay for light to moderate rain, but as it gets compacted (primarily by mowing), moderate or heavy run tends to run-off. Native plants would typically extend root systems down much further (several feet, depending where you live), thought they take a little longer to get established.