Actually, there are even opinions that one should not read along. The Zohar[2] states that only one person may read from the Torah at a time. However, this source likely does not preclude an oleh[3] from reading along, for one or more of the following reasons:[4] 1) The Zohar may have objected only to someone else reading along audibly,[5] whereas an oleh should be reading so quietly that he cannot even hear himself.[6] 2) The Zohar referred to Talmudic times, when the oleh also lained, so that there was no need for anyone else to read.[7] 3) We base our rulings on standard halachic sources whenever they contradict the Zohar.[8]
Let us indeed investigate several halachic indications and sources. The Rosh[9] writes that if the oleh does not read along, his beracha is l’vatala,[10] as it does not make sense that A makes a beracha on a Torah reading that B carries out. The Talmudic system, whereby the oleh himself lained aloud for the community, is fundamentally ideal. Our practice of giving the recitation of the berachot to the oleh and assigning the reading for the community to a ba’al korei is a consequence of the fact that not everyone who is deserving of an aliya knows how to lain proficiently. The Rosh writes that while an oleh must read, he does not need to know how to read independently; he can be helped by following along with the ba’al korei.[11] The Beit Yosef[12] concludes that according to this compromise position – which permits giving an aliya only to someone who is capable of reading from the sefer Torah, but even with help – the blind or others who cannot read a Torah scroll at all should not receive an aliya. Even if he can repeat after the ba’al korei, it is forbidden in the context of Torah reading for one to recite what he has not read from a sefer Torah.
Acharonim question the view of the Rosh/Beit Yosef. Given the broad halachic rule of shomei’ah k’oneh,[13] since the oleh is listening to the ba’al korei read, why isn’t it considered as if he is reading along? Indeed, the Maharil[14] and the Taz[15] disagree with the Rosh’s view and maintain that a blind person may indeed receive an aliya. The Taz cites as proof a Yerushalmi[16] that states that one person can make a beracha on the Megilla even when the reading is done by another.
Rav Yaakov Emden[17] supports the Rosh’s approach by asserting that shomei’ah k’oneh, as applied to relating the spoken text to the listener, is insufficient here. Since the laining must be read from a Torah scroll, the oleh must read it from the scroll (at least with his eyes), which a blind person cannot do. The Bi’ur Halacha[18] deflects the Taz’s proof from the Yerushalmi by distinguishing between the cases. Regarding the Megilla, the reading and its berachot are the obligations of the entire congregation. Just as every individual can listen to the ba’al korei’s reading in order to fulfill his obligation, he can listen to anyone’s beracha to fulfill that part of his obligation. In contrast, the beracha on Torah reading was instituted specifically for the one who is called to read from the sefer Torah, not for the rest of the congregation, even though they listen to the reading. (Other explanations of the Rosh are beyond our present scope.)
How do we rule? The Shulchan Aruch,[19] following the Rosh, writes that a blind man should not receive an aliya. The Rama[20] counters that nowadays, since the ba’al korei does the reading on the congregation’s behalf, it suffices that he read from the scroll, and the oleh can therefore even be blind or illiterate. Many Sephardic communities follow the Rama.[21] However, in ordinary circumstances, when the Shulchan Aruch[22] states that the oleh must read along or be guilty of a beracha l’vatala, the Rama does not dissent. Is there a tacit contradiction in the Rama? The Bi’ur Halacha[23] assumes that the Rama also prefers the Rosh’s ruling and relies upon the Maharil’s leniency only in the case of the blind and illiterate. Since they cannot read along, depriving them of ever having aliyot would embarrass them and might cause acrimony.
Regarding your question, then, you are certainly acting properly. Apropos those who do not read along, it is the rabbi’s prerogative and obligation to decide if, how, and when to educate them or deal with the possibility that their aliyot do not count. From your perspective as a member in the congregation, remember that the ruling of the Maharil, the Rama, and others can be relied upon b’di’eved.[24]