What explains why obligatory Hajj does not recur every year merely because the House remains?

Causes of Legal Obligations: Time, Worship and Purification

• Hajj’s cause necessarily arises as an entirely new cause each year
• The duty is specified once in a lifetime; persistence of the cause does not multiply it
• The first Hajj turns every later Hajj into a make-up obligation
• One occurrence of ability necessarily produces an annual new duty