Most likely his obituary doesn't list that info either. It might have listed surviving siblings. His Social Security application may have the parents' names as might his marriage record.
Pittsburgh did record city births starting in 1874 but not all births were recorded so don't be surprised if it is not there: http://www.alleghenycounty.us/wo/cert.aspxhttp://www.alleghenycounty.us/wo/cert.aspx
Charlie K. Simpson's WWI draft card shows him born in 1881 while his death certificate has him born in 1882.