The banking domain has been there since the beginning of computing.
IBM was premier supplier for mainframes. Most of the Banking and Flight services was served using infamous AS/400 platforms which looks like this.
It evolves from punch-card, typed mainframe.
Later, it's updated and renamed to IBM System i, and now it's IBM Power Systems. As a platform, AS/400 and later IBM System i can be virtualised and it's 64-bit from the start.
The language running on this platform is COBOL and later Java. Migration from this system to newer systems will be very costly.
x86 itself has never been seriously considered as powerful server platform until IBM xSeries x440 that drive adoption of x86-based server, and it was just happened recently as in 2002, less than 30 years.
Until circa 2010ish, no banking and telco will use x86 as server, they'll order iSeries or pSeries.