Because it doesn't make sense to do so. If you think about an index in a book, the keys are short. NText is a blob store for large amounts of text data. Even if it could be an index key, it wouldn't be at all useful.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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