I use screws & lag bolts in a dry joint with damp/wet wood, fully expecting everything to shrink in my Frankenfurniture. I was right.
The legs are a bit wobbly, tighten the screws. Maybe this coming winter, I'll drill out the screw holes at 3/8" and peg and glue the joints.
Its a carving bench 12" x 48", built entirely out of 4x4 western red cedar (crappy small-log stuff, far harder than the fancy deck & furniture grades.) Easy shopping when the mills are side by side and 20 minutes from the house.
A decade ago, I built myself a simple bedside table. Dimension lumber, nothing fancy. Glue, dowel pegs and clamps. Clock radio, some books, that's it for load. It will last forever.
No, I have no idea why builders use both glue and screws, especially if the unit takes little load.