The 1♣️ opening in Standard American is an opening of convenience. Hands that don't fit in other more well-defined openings are opened with 1♣️. The 1Nt opening takes care of Balanced or semi-balanced hands with 15-17 HCP; with 5+ cards in a Major suit, one opens 1♠️ 1♥️; and with length in Diamonds, one opens 1♦️. The 1♣️ opening covers all other 12-21 HCP hands. What does that mean for opponents?   

This video presents Purvapaksha of the Standard American 1♣️ opening. As you can see from the figure, about 1 in 10 hands, opener's longest suit will be Spades; on 1 in 10 hands Hearts' and on 2 in 10 hands, one of the Majors will be as long as Clubs. Only on 6 out of 10 hands will the Club suit be opener's longest suit.

 

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Where Club suit is not the longest of the opener, one of the opponents might be short in that long suit. If the Left Hand Opponent is short, he will face difficulties in bidding simply because common bidding methods are predicated on double showing tolerance for ALL unbid suits.