To put it bluntly, requirements text is typically pretty bland to read. You don’t get the colorful variety of writing in passive voice, because it can confuse the audience. But also, you have to pick your words very carefully. English is actually quite challenging, in that words have different meanings.
There is a concept called Garden Path Sentences that illustrates this well. And the essence of it demonstrates how people read sentences one word at a time. If something doesn’t make sense in your intuitive first reading, you have to back up and re-read it. The example they give is:
The horse raced past the barn fell.
Technically this is a correct sentence, but it takes two readings to have it make sense.
This certainly something we want to avoid in writing requirements, and so we write in active voice with simple obvious word choices. Bland yes…but also very practical!