Weeds offer shelter, oxygen and food for insects, minnows, crustaceans and panfish and that attracts the bass, northern pike, walleyes, musky, etc. You get the point--any lake that has weeds and a walleye population you can bet the weeds will hold fish.
This is especially true in stocked lakes. These are usually waters with no or marginal spawning habitat. Those lakes are usually lacking rocks and gravel so most of the structure is weed beds. Walleyes will go where the food is and that means they spend a lot of time around and in the weeds.
Next week I'll discuss techniques for fishing in and around weeds.