I think it's that spreadsheets leave a lot of "real programming" out, even though they may be computationally complete. A spreadsheet is a way of orginizing data, so the language used within should be specialized in handling data, like formatting it and running formulas on it. Excel doesn't need a full GUI API embedded in its scripting language, so it doesn't have one. This is generally considered a good thing.

In other words, a spreadsheet has left a lot out of its scripting support, and this is a good thing. So good that people don't even realize that they're programming.