Here is an example of bad technical writing, Cake Left Out in Break Room With No Instructions. Yes, we realize it is a piece of satire written by the Onion.
However, think about it. What if a cake had appeared in the break room with nothing written on it, no one knowing why it was there, or who it was for, there would some serious confusion.
Now imagine, that cake is software with no instructions, a pretty resume with no structure, a business or marketing plan with no goals, a marketing flier with two little or too much information, an employee manual that hasn’t been updated. Not so funny now.
Instructions no matter what they are pertain to need to be clear and concise; even if it just a cake sitting in the break room.