Yeah I use it. The same reason people store money in their savings and don't leave it all in checkings lol, just for the purpose of saving up. I would like to buy some collectibles that i know will be expensive so i just store some away after I go over like 300 bells or something. I leave some bells out for when I see art I want to purchase on here.
AlSO i've seen users leave others VM's asking to borrow bells when they have a lot & I feel like when you're buying stuff on here if you have a fat chunk of bells people expect you to pay more.
Before seeing this thread I didn't even know it was a feature here. Now I'm planning to use it in the future if I get the need to save TBT for something just so I wouldn't end up spending them on something else.