I went to a mass at my uncle’s church this weekend and noticed that when we went up for communion, some people (about 4/5 out of the 25/30 in the congregation) took only the bread and not the wine.
It used to be the standard way to serve communion to the congregation was to give out only the bread – stick out your tongue and let the priest place the wafer on it. At most, he would dip the host in the cup. So for a majority of congregants it is still the traditional way of doing things – it not being mandatory to take communion in both forms.
“pastoral reasons” = practical considerations, some of which have been mentioned in the prior posts. Also: you can relatively easily carry around and store a large stock of those little unleavened wafers so as to have enough for however many people show up, and equally safekeep (separately) the already-consecrated ones if there are left over; just keep them dry and secured from vermin. Doing the same thing with wine requires a bit more logistics for transportation, storage, and security.
It’s rare that I attend a Mass when the wine is offered; when it is, I rarely partake. As has been noted above, receiving communion under either species, alone, is sufficient – there is no extra spirtual benefit for taking both.
When I was still going to Catholic Church, we had several members of the congregation who still went by the “old” way of Communion - kneeling at the communion rail, accepting the host on the tongue rather than the hand, and not partaking of the Blood.
You would be surprised how many of the older generation of Catholics still refuse to accept the changes made to the Mass as a result of Vatican II. We even had one parish (don’t know if it’s still around anymore) that was strictly pre-Vatican II - All Latin Mass, the priest faces the altar rather than the congregation, etc.
Catholic belief is that the body and blood are both present in both the bread and the wine, so consuming either one is sufficient. (Cf. The Baltimore Catechism, Q. 881-882)