[mehrdadn]

A couple of considerations that come to mind for a database: (a) efficiency, and (b) dynamicity. The tree structure isn't particularly efficient (it has a lot of space overhead, and I think it's also not as fast), so you'd prefer something else if possible. So people often use suffix arrays + LCA preprocessing instead. However, those are hard to make dynamic (your database is constantly changing), so I'd expect that still makes it tough to use them in databases. Though I suspect this isn't the whole story.