I don't, but I sometimes see them used here in Japan. Some small-shop operators use them to add up charges and show the total to the customer. I was recently in the office of a small company, and I noticed that the bookkeeper had a calculator next to a pile of paper (receipts?) on her desk. She also had a computer in front of her with a spreadsheet on the screen.
When I moved here forty-three years ago, it was common to see abacuses used in similar situations. There's still an abacus school [1] not far from where I live, but it's been a long time since I saw one in use.
Back in the (early 1960s?) Isaac Asimov wrote a book on how to do arithmetic calculations in your head. He pointed out that someone who developed that skill could solve problems faster in their head than by reaching for a slide rule, and they wouldn't necessarily be limited to slide rule approximations. Engineers, accountants, etc. would be more productive by being able to do calculations without having to reach for a slide rule or pencil and paper.
[pause for 'slide rule' chuckle]
The same applies to "open calculator app and key the figures in," though. I'm not sure that "user interface" was a thing back when he wrote that, but that's what he was talking about.
That’s one reason the abacus hasn’t been completely replaced by calculators: some abacus users become able to calculate very quickly in their heads by visualizing the changing bead positions. In Japanese the skill is called 暗算 anzan, literally “dark calculation.”
(I'm in the US) I remember being taught how to use an abacus when I was in grade school. Not kidding. I'm not so old that they were used anywhere in real life. I believe the whole point was to teach different ways that calculating can be done. A little horizon expansion.
When I moved here forty-three years ago, it was common to see abacuses used in similar situations. There's still an abacus school [1] not far from where I live, but it's been a long time since I saw one in use.
[1] https://maps.app.goo.gl/nvTg4hfSjTcba47c8