For critical systems, reliability, predictability, consistency, and long-term performance data are more important than modernization. It makes perfect sense that a system like this would lag the leading edge of technology significantly. It is ok if the technology has problems, even if it has high failure rates, as long as the failure rates are predictable - then you can write procedures around them. Floppy disks don't exactly offer bulletproof reliability, but they are well understood - and also you can generally just toss them on a desk or in a drawer without worrying too much about incidental damage.
You want this kind of technology to be so simple and dependable that you don't have to think about it, it just works as expected. It also massively simplifies staff training and procedure documentation if the relevant bits of technology don't change very often - until of course those bits become so outdated that the procedures for getting them to interface with newer systems becomes its own mess.
If it ain't broke, don't fix it.