The free-form nature of spreadsheets, in my experience, almost always makes for human readable repositories of data that are nearlyuseless from an automated processing perspective. I cringe when I'm asked to export data from a database into a spreadsheet for users to edit, because I know I'm going to get back an unparsable mess that I'm going to have to invest time in to make usable again.
The spreadsheet is, effectively, shifting the user's inability to understand why data needs to be organized well off to a programmer (or some other grunt) who ends up fixing all the data up. (Or, alternatively, nobody fixes it up and the business ends up making bad decisions based on garbage data that came from a spreadsheet that's a disorganized mess.)
Edit: Grammar.
Well said...it's that concept of machine-readability that is so core to efficient data investigation and interoperability with other enterprises (such as web apps)...theoretically, such a concept is learnable without a decent jump into the computer science/programming waters...but honestly, I haven't run into many lay persons who have figured it out well enough for themselves.
The reason Excel is so popular is not because non-coders are dumb. It's because "tools" provided by IT department are usually piece of crap that makes work more difficult for people using them. Take using Excel instead of databases - why spreadsheet is better? Because it has easier data entry, and it's free-form. When you need to modify your workflow to include some additional notes, you don't have to write to the manager of the manager of the internal procedures to maybe consider updating the schema somewhen before next decade. You just add a new column and you're done.
I'm sure when someone creates a program that actually solves the problems those people encounter every day, they'll gladly switch to using it. But it's easier to say that users are stupid instead of actually caring about what their needs are.