I am learning to use CDC in SQL server 2008, I have read that LSN is always incremented and is based upon timestamp, so why LSN is required, if it is calculated from timestamp which can be used as increamental sequence id for changes made. I am sure that there will be some other purpose as well of lsn.
A date/time value is generally not considered to be unique enough. No matter how fine you define it, it is possible to have 2 actions occurring for the same datetime value.
From another view, time is is a real number. No matter how accurately you store a time, there is always some rounding to your level of resolution (In this case, 3.33 ms or 100 ns)