For me I like to weed out plants that visually look like they're competing with a nearby crop, plants that are going to seed soon, or any grasses, from the garden beds.
If a lambsquarters is growing up by an onion, yeah gonna pull it out or the onion will get out competed easily. If it's growing by a kale that's 2 or 3 times bigger, that lambs quarter plant will not harm the kale in my opinion.
All plant roots will make the soil around them a little bit nicer, more wet, fertile, alive. So if you have a weed growing where it's not currently hurting any of your plants, you might as well leave it for later, as a mini cover crop