Generally, I think it's very much both. People's expectations for what's possible is based on experience. And that experience is driven by by previous expectations.
I've helped some places shift to a much faster delivery cadence. That's really easy to do if you have a clean slate. E.g., when I co-founded something in 2010, we started with a weekly delivery cadence and the turned up up, so that a team of 6 was shipping 2-3 times per day. Our infrastructure and our code was very much tuned for that. It took some work to get to that level, especially in terms of automating absolutely everything, but once we'd done the work it was fine. In fact, it was great!
In contrast, I've tried to get existing companies just up to a weekly cadence. That's an incredible slog because expectations, tools, and processes are all built around much slower cadences. It's not like anybody was bad. It was just that if you were only doing something quarterly or annually, it made no sense to automate it. Or even understand it, really. There was a lot of the business version of, "Honey, where did we put the Christmas lights? Did we replace the wonky tree stand, or did we just talk about it?" It's a nightmare. And the whole time most people are like, "Why are we bothering to go faster? The old approach worked!" And for them, it did work.
For a lot of government stuff, I think the change cadence co-evolves. Law is pretty stable, so people just build with low change frequency in mind. A decade later a change comes along and it's really hard, so the higher-ups learn to minimize change. That makes things even worse; requests are now met with high budgets and long lead times, meaning legislators learn not to propose small improvements. That legal stability biases the tech staff and processes even more to not touching anything.
And of course, so much of this stuff was built long before we figured out how to maintain quality in the face of frequent change. Two decades in, there are a ton of new companies that still can't do CI/CD and automated testing well. It's no shock code from the 1970s hasn't caught up.