Actually, there is a difference between encouraging a practice and permitting it. Consider this guidance from Redemtionis Sacramentum (emphasis added):
“100. So that the fullness of the sign may be made more clearly evident to the faithful in the course of the Eucharistic banquet, lay members of Christ’s faithful, too, are admitted to Communion under both kinds, in the cases set forth in the liturgical books, preceded and continually accompanied by proper catechesis regarding the dogmatic principles on this matter laid down by the Ecumenical Council of Trent.”
The clear implication of the emphasized text is that reception under both forms, while permitted, is the exception rather than the rule.
Also, it’s worth noting that the prospective number of communicants is not the only factor in determining the appropriateness of offering the Sacred Species under both kinds, even in cases where it is permitted. Paragraph 102 of RS gives a more comprehensive list:
“102. The chalice should not be ministered to lay members of Christ’s faithful where there is such a large number of communicants that it is difficult to gauge the amount of wine for the Eucharist and there is a danger that “more than a reasonable quantity of the Blood of Christ remain to be consumed at the end of the celebration”. The same is true wherever access to the chalice would be difficult to arrange, or where such a large amount of wine would be required that its certain provenance and quality could only be known with difficulty, or wherever there is not an adequate number of sacred ministers or extraordinary ministers of Holy Communion with proper formation, or where a notable part of the people continues to prefer not to approach the chalice for various reasons, so that the sign of unity would in some sense be negated.”
Hope that helps.