Believe me or not, I use it 10 years with my wife and don’t see what additional info web version can provide. And for sure in this case your data wouldn’t be privately stored, then you need a registration… and so Monetal wouldn’t be different from many many similar apps.
I am honestly not bothered by having an account, it's just that sometimes it would be much faster to fill in entries on the computer and my current app only has mobile variants and slow animation transitions. It can get infuriating.