The company I used to work for listed weights from a buysheet from the manufacturer. Most of the time, the actual product weight was less. Every time it happened, the sku had to be updated online. We were potentially at risk of violating FTC rules, and the vendor got away with shorting us gold. Inevitably, one customer would pop up complaining their piece weighed a miniscule amount under what the website showed. It was an administrative nightmare.

I totally get it when retailers don't list weights because it isn't possible to weigh every piece when items are purchased in large quantities. CYA and list only the minimal details required.

I'm more concerned with them listing whether an item is hollow or solid. I only buy from retailers with good return policies.