I've seen this talked about briefly on Discord, but I didn't see it posted here, other than a _similar_ but not-quite-the-same post here: viewtopic.php?f=12&t=11872&p=98543&hili ... ant#p98543 (Feel free to merge these posts if desired)
Essentially, while it seems quite natural to enchant a lasso for the weight reduction (since unenchanted it weighs 10 pounds), the moment the lasso is used and then retrieved (e.g. after climbing over an obstacle), a "default" lasso is given back to the player, thus wasting the 10% enchantment.
I know this is only a minor annoyance, but for us Dex-oriented PCs, every pound of inventory space is sacred

Thanks!