Lightweight furniture is very common.

IKEA and its competitors sell huge amounts of lightweight furniture every year.

Differences in weight can also be a distinguishing factor between well-built, durable furniture and look-alikes that are more cheaply made.
For example:

• An 80″ sofa made with a plywood frame and sinuous wire foundation selling for $699 may weigh around 120 lbs.
• A similar looking sofa made with a 5/4″ solid maple frame and 8 way hand tied coils selling for $2500 should weigh over 250 lbs.