Drawer bottoms must remain free-floating (not glued to the drawer frame) to allow for expansion and contraction due to changes in humidity. But often the bottom will develop a rattle.
joinery shop tip

Apply a fillet of silicone sealer along the dadoed joints where the drawer bottom fits into the frame. The flexible silicone sealant will silence the rattle, yet still allow the drawer to expand and contract as it needs to.
—From the WOOD® magazine shop