The reason popes tend to be so old is largely due to the long hierarchical process in the Catholic Church, where prospective popes are almost always cardinals first, and becoming a cardinal requires becoming a bishop, which takes many years. This means most candidates are already quite advanced in age when they are elected. Additionally, the cardinals who elect the pope often prefer an older pope to limit the length of his papacy, as longer reigns by younger popes could lead to an outsized impact on the Church for decades. Older popes are seen as bringing wisdom, and the election of older popes also fits with the fact that the cardinals themselves tend to be older. Moreover, improvements in modern health and life expectancy allow older popes to serve effectively even at advanced ages. Historically, the average age of popes at election has been around 62 to 70 years, with some exceptions on either side. The Church is not opposed to younger popes, but the process to rise through the ranks takes time, and there are practical and traditional reasons behind selecting senior candidates.

Summary:

• Popes are usually elected from among cardinals, who tend to be older due to a long career progression.
• Cardinals often choose older popes to have shorter papacies and prevent extremely long reigns.
• Older age is associated with wisdom and experience for leading the Church.
• Improvements in health have allowed older popes to be effective leaders.
• Average election ages are generally in the 60s or 70s.

This explains why popes often appear old at the time of their election.