Navigating my filesystem every time I need to upload something to a website is a time-consuming pain. If upload fields provided some kind of hint about what file the user will upload to the website, the web browser could use that to open the file browser into what would likely be the appropriate folder containing said file. For example, when I need to upload my resume into a job application form, I click the button to upload my resume and the file browser opens into my home folder, from which I need to navigate to the folder to my career file before double-clicking my resume to upload. If the webpage provided a simple query for the appropriate file, the browser could likely guess that the 'career' folder or the folder that contains a file named 'resume' would be the appropriate folder to open the upload file browser into.