[kw71]

> while open source keeps adapting and changing

In these places, this is a great thing to avoid. Old software is well known. You do not want to be the one to be affected by a bug that stops production or changes data.

> mainframes have remained stagnant in features

Having a well known universe without any beta software, and not being disrupted by new stuff that you don't need anyway, is a damn good feature.

[derekp7]

Meanwhile, some small startup is using newer technology that makes them many times more efficient. And allows them to utilize their IT as a core part of their product, instead of an internal utility service. And stealing all your customers.

Of course, there are industries that are immune to startup competition due to the high barrier of entry (banks, insurance, governments). I don't think it is a coincidence that these are about the only environments where mainframes are still dominant.