The reason it was done that way originally makes sense: they didn’t want to have to write 50 stored procedures to access the data
In retrospect, if I’d known of the web page, we could have come up with a Stored Procedure that did this, albeit with either dynamic SQL or with the SP hitting a view that consolidated the tables.

There is a stackoverflow case on it, albeit with no responses. http://stackoverflow.com/questions/13077537/how-to-make-sqldatasource-insert-into-view-instead-of-the-underlying-table

Triggers aren’t always a bad thing. But they can have significant gotchas.

Digressing a bit here, but you’ve hit on one of the reasons that triggers make me uneasy. Triggers are not bad for their own sake, but they’re a symptom that something else is wrong. In your case as you’ve found out, you’re already very very aware of what’s wrong. It’s just that you don’t have control to do anything about it. And that’s always frustrating.

TL;DR : __make__ your web devs use SPs. Don’t let them insert into a table directly.