Bad habit, I agree, but probably due to certain companies' very-effective marketing. For example, in some areas of the country, people used to commonly refer to carbonated beverages as "Coke".

"I sent you a file".

Okay, which one? Can you be more specific? I have four files that you sent. Saying "I sent you a Word file" isn't too much information, it's just the right amount of information.

As for saying the brand name, text documents vary far and wide. I wouldn't ask someone to open a docx in Wordpad or Notepad, it'd either be horrible formatting or useless noise. Even opening a docx in OpenOffice could turn out poorly, depending on which features of Word you used in the creation of the document.

If someone was asking if they could ride with me, it makes a big difference if I drove here in my Hyundai Accent or if I rode here on my Schwinn.

Word file is both more specific and shorter than text document.

Your analogy is horrible because one way to drive implies only one kind of file. Try "I drove here." "I took a bus here." "I took a taxi here.". And if they have multiple cars it's especially reasonable to say which one they took.

I really don't understand why you have this complaint. Do you have some kind of weird overattachment to genetic terms?

Let me google that for you. We are just as guilty.