Well it depends on your understanding of how the sacrament works. A basic assumtion is that the recepient has faith in order to receive it. If, lets say, you need to go get some water, is it more effective to collect it in a strainer or in a basket? Well the ‘intactness’ of this bucket comes from faith. The majority of people have poor to no faith, so if you send a person without faith to mass they will tell you that they stopped believing in magic as a child.
Now if you read carefully what I said, I write using very specific words, you will see that I meant the following. Based on a quick google search the word efficaciousness has the following definition: “having the power to produce a desired effect,” What I wrote is not that the sacrament magically becomes more efficacious, but that it its effectiveness is made more apparent. Why? Because for those that go they are able to collect water using a bucket instead of the strainer. Now if for you the bucket is already at hand then go on to the regular mass, but for the majority of people, those who are not in church to whom we have a duty to look for, their faith does not exist in such a way which can receive the graces given them by the sacrament.