I was asking myself why today's feast of Our Lady of Mount Carmel is a universal feast of the Church. But, why, then, is the feast of Our Lady of the Rosary a widespread feast? Because of the popularity of the devotion is a good approximate answer. Go to Mary for help is a certain gesture of dependence.
The feast recalls a 1226 victory over enemies of the Church and the Carmelite friars, and it also recalls the reception of the scapular by Saint Simon Stock on this date in 1251.
By the 14th century the proposed feast received approval of the Roman Pontiffs Honorius III and later by Sixtus V; over the years it has been questioned by ecclesiastical figures and found to be appropriate for the Carmelite order with a proper vigil Mass and a privileged octave.
Our Lady of Mount Carmel's feast is another feast of the Virgin Mary that focuses our eyes on the Lord. And, we can never have a enough of that.
You may be interested in reading this piece on scapulars.