> As such, you can have good memory access patterns even in a high language like Java or C#.

CPU and data intensive heavy lifting is rarely done in such programs, it is delegated either to specialised libraries or some middleware in the form of a RDBMS. Most of these programs spend most of their time waiting for some IO event, so the few microseconds gained from the vector with a few hundred elements are negligible.

> But you can read a file from beginning to end.

That's what most programs actually do most of the time because files are essentially a stream abstraction. Programs that jump around a file would map it into memory, then the CPU and the kernel would do their best to cache the hot regions, even if the access to these regions is temporally or spatially distant.