Standard SQL is rubbish for time series queries as it is based on set theory which does not have order. Most SQL datbases exploit that fact to increase performance. Fundamentally kdb is based on ordered lists, which is a much better paradigm for time series data.

The contrasting queries can be seen here: http://www.timestored.com/b/kdb-qsql-query-vs-sql/

I do agree they could use competition as the overall offering is weak but the core database is very strong.