Why doesn't the Catholic Church give indulgences to everybody, regardless of their works? In learning about indulgences, I started to wonder why a work was necessary for the giving of an indulgence. In looking at the Catechism of the Catholic Church, it appears to me that a work is necessary because the Church chooses to make it necessary (italics mine):


  Obtaining indulgence from God through the Church
  
  1478 An indulgence is obtained through the Church who, by virtue of the power of binding and loosing granted her by Christ Jesus, intervenes in favor of individual Christians and opens for them the treasury of the merits of Christ and the saints to obtain from the Father of mercies the remission of the temporal punishments due for their sins. Thus the Church does not want simply to come to the aid of these Christians, but also to spur them to works of devotion, penance, and charity.


I'm not really sure that I understand this view. Of course, these works of devotion, penance, and charity are good things, but it seems like it would be more compassionate to give out indulgences to everybody so that they do not suffer from punishment for their sins in purgatory, and find other ways to encourage people to do these works. Indeed, there seems to be a similar argument in Thesis 82 in Martin Luther's 95 Theses:


  Why does not the pope empty purgatory for the sake of holy love and the dire need of the souls that are there if he redeems an infinite number of souls for the sake of miserable money with which to build a church?


I realize that this thesis was addressing the idea that "when the coin in the coffer rings, the soul from purgatory springs" and and other abuses of indulgences. But the sentiment seems to match the question I am asking: wouldn't it be more merciful if the pope were to choose to grant indulgences to everybody, thus reducing the suffering of those in purgatory (or empty it entirely) regardless of their works?
The Council of Trent, which condemned Luther's errors and heresies, wrote this on 4 December 1563, in its 25th session, "Decree Concerning Indulgences" (see my emphasized parts):


  Whereas the power of conferring Indulgences was granted by Christ to the Church, and she has, even in the most ancient times, used the said power delivered unto her of God, the sacred holy Synod teaches and enjoins that the use of Indulgences, for the Christian people most salutary, and approved of by the authority of sacred Councils, is to be retained in the Church; and it condemns with anathema those who either assert that they are useless, or who deny that there is in the Church the power of granting them. In granting them, however, it desires that, in accordance with the ancient and approved custom in the Church, moderation be observed; lest, by excessive facility, ecclesiastical discipline be enervated. And being desirous that the abuses which have crept therein, and by occasion of which this honorable name of Indulgences is blasphemed by heretics, be amended and corrected, it ordains generally by this decree, that all evil gains for the obtaining thereof,—whence, a most prolific cause of abuses amongst the Christian people has been derived,—be wholly abolished. But as regards the other abuses which have proceeded from superstition, ignorance, irreverence, or from whatsoever other source, since, by reason of the manifold corruptions in the places and provinces where the said abuses are committed, they can not conveniently be specially prohibited, it commands all bishops diligently to collect, each in his own Church, all abuses of this nature, and to report them in the first provincial Synod; that, after having been reviewed by the opinions of the other bishops also, they may forthwith be referred to the Sovereign Roman Pontiff, by whose authority and prudence that which may be expedient for the universal Church will be ordained; that thus the gift of holy Indulgences may be dispensed to all the faithful, piously, holily, and incorruptly.


Granting indulgences "by excessive facility" makes "ecclesiastical discipline be enervated" (enervetur: weak, unmanly, effeminate). The Church, however, wants strong soldiers for her exultation and God's glory. Her supreme law is the salvation of souls, not the confirmation of the faithful in their sins.