Supporting old architecture takes A LOT of engineering effort for complex physical devices, creating new architectures from scratch with the learnings from the old architectures often costs too much (and you still need to support the old systems for a long time anyway).

I worked in a project where an architecture was very flawed initially and took almost a decade to move away from it.

So often management pushes for incremental updates on an outdated architecture because the risks are too high since the new architecture might have all new problems of its own.