Contrary to common misconception, abstinence from meat on Fridays throughout the year has never been abolished from Roman law. It was not abolished by Vatican II. It was not abolished by Pope Paul VI or Pope St. John Paul II. It was not abolished by the 1983 Code of Canon Law. It remains the universal law of the Latin Church — even if not everyone has to obey it.
Per the 1983 Code of Canon Law:
Can. 1249 The divine law binds all the Christian faithful to do penance each in his or her own way. In order for all to be united among themselves by some common observance of penance, however, penitential days are prescribed on which the Christian faithful devote themselves in a special way to prayer, perform works of piety and charity, and deny themselves by fulfilling their own obligations more faithfully and especially by observing fast and abstinence, according to the norm of the following canons.
Can. 1250 The penitential days and times in the universal Church are every Friday of the whole year and the season of Lent.
Can. 1251 Abstinence from meat, or from some other food as determined by the Episcopal Conference, is to be observed on all Fridays, unless a solemnity should fall on a Friday. Abstinence and fasting are to be observed on Ash Wednesday and Good Friday.
Note the reasoning: Penance is not man’s idea, but God’s.
Meatless Fridays are a small sacrifice.