All my personal files are kept in plain text format. So please do not ask for my resume in the Word format - such requests will be silently ignored.
People create their files for future retrieval and reuse.
E.g., today you might write a paper which you will print tomorrow, send via e-mail to a friend the next day and incorporate his remarks the next week, then you might want to retrieve your original text without his changes. If your data is saved in a proprietary binary format, these simple tasks are complicated beyond your wildest imagination. PostScript, understood by all modern printers, is here to save your butt. He would also have to own a tool which understands your particular idiosyncratic proprietary binary format. You are stuck with the application-specific functionality.