Even small banks. Basically every bank that was around 20 or 30 years ago started with mainframes (or very large minis) and still uses them. I'm not in that business, but I've seen the server rooms, and I haven't heard of a bank switching over to a rack of PCs, yet. There might be, but that would still hundreds, perhaps a thousand banks in Europe alone running on large-ish iron.
There might be less mainframes in total, though. The bank where my parents worked had 4 at different sites, but now runs on a single one, AFAIK.
