The beauty of Excel is its ability to do many things 'well enough' in a way that is accessible to a lot of people.
My dad put together his architectural plans for a new house in Excel because it is a tool with which he felt comfortable. Some people do calendars in Excel while others try and recreate a full General Ledger system. Because it works well enough, people don't see the need to invest the time in learning a new application and instead invest their time in pushing the limits of the tool.
As someone who builds financial models and who audits those built by others (and is a competent programmer by night), I think that the key source of risk in Excel models is that the tool has no knowledge of intentions. What I mean by this is that if I'm building a cash flow model or if I'm doing a pixel drawing, Excel doesn't care; as users, we are forced to create our own structure and build in our own checks and balances. If I make a balance sheet in Excel that doesn't balance, Clippy won't show up and let me know that things are broken.
I've often thought that it would be really amazing if a semantic layer could be built that uses Excel as the calculation backend. This sort of tool could understand the sorts of concepts of financial statements, projections, time-series and other concepts that often show up in financial models. It would have a built-in understanding of the domain-specific models that would let it leverage that understanding to reduce risk in the building of financial models. If I told it that I wanted to add a revenue stream that is tied to the output of production, the tool would connect the dots between the production schedule, any inflation and/or foreign exchange assumptions and would feed changes in working capital according to the associated collection terms, etc...
Before I get too carried away, the point is that this type of semantic layer would be much better at preventing and detecting anomalies and potential errors in the development of a high-risk financial model. Does anyone have experience with any such tools?