EDIT: I'm serious. I can think of several reasons why I would not want to use this, ranging from "I don't want to have to remember a specific URL for this one purpose" all the way up to "I don't want to be sending my invoice data over an unsecured connection to some random statup-of-the-month."
- Discoverability: when I was working on my invoice template, I looked all over the web, and found a bunch of garbage, before I eventually hand-crafted something in Excel
- Ease of use: Word templates can be annoying to fill out and format right, and they won't do the math for you. Excel will, but good luck getting it to print right every time, and heaven help you if you need more than one page.
- Fun: When was the last time you filled out a Word template and thought, wow, that was kind of cool!
I joined a small business that was doing them in Word. After reviewing the last 12 month of invoices (about 200), I found about 5% of them had simple math errors, i.e. the Total did not match the sum of the line items.
Sure, you can get it right by hand, but why bother when using software can eliminate the adding-up step entirely?
I'm a little concerned about whether or not you know this and just forgot for this simple example, or don't know this about how web apps work. You should just assume that any web app you're using is collecting your data, even if you don't "save" or setup an account.
EDIT: I assume this because I have written ones that maximally collect data, so I just assume others have done the same.