FLC OF AN SMT CPR JET FORGOT TO OBTAIN LNDG CLRNC.

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CLRED FOR VISUAL APCH TO ARPT APPROX 20 MI OUT (FROM NW). CONTACTED TWR AFTER BEING HANDED OFF. INSTRUCTED TO RPT 5 MI N OF ARPT FOR RWY 18. DISTRS FROM PAX DURING THE VISUAL APCH INTERFERED WITH PERFORMING THE BEFORE LNDG CHKLIST; THOUGH IT WAS COMPLETED IN ITS ENTIRETY. HOWEVER; I FAILED TO CONTACT THE TWR AT 5 MI. THE CAPT CONTINUED THE APCH AND AS WE CROSSED THE THRESHOLD; IT OCCURRED TO ME THAT WE WERE NOT CLRED TO LAND. I BROUGHT THIS TO THE ATTN OF THE CAPT; BUT HE ELECTED TO COMPLETE THE LNDG RATHER THAN INITIATE A GAR. AS WE TURNED OFF; THE TWR MENTIONED THAT 'IT WAS CUSTOMARY TO RECEIVE A LNDG CLRNC PRIOR TO LNDG AT THIS ARPT.' THOUGH WE WERE NOT REQUESTED TO DO SO; WE PHONED THE TWR LATER TO APOLOGIZE AND WERE TOLD THAT WE WERE IN SIGHT THROUGHOUT OUR APCH AND THAT THERE WAS NO PROB. HOWEVER THANKFUL THAT WE WERE NOT VIOLATED; I WOULD HAVE PREFERRED THAT THE TWR QUERIED US SINCE WE DID NOT RPT IN AS INSTRUCTED. THIS WOULD HAVE ELIMINATED THE POSSIBILITY OF A LAST MIN GAR ATTEMPT.