They don't care about Coptic Orthodox Christians because Western Christians (Catholics, Protestants, and to some extent EO -- sorry, OP, but even though we have better relations with your church now than before, and I know that you and many other EO Christians personally do care a lot, it must be said that EO have historically attempted to use Coptic misfortunes as a pretext to try to get us to unite with them, such as the Russian ambassador at the time of HH Pope Peter VII in the 19th century slightly before the gizya tax was abolished, who offered 'protection' for the Copts if they would unite with the Russian Church and was told by HH that, no, our only protector is God) have spent centuries thinking of us as heretics and/or pagans and attempting to convert us by the worst ways, and hence whenever our churches or people are thought of at all it is generally with that in mind first, and everything else second. There is the famous story of the Presbyterian missionaries in dialogue with the bishop of Asyut in the 1860s who were asked by HG "Our people have been living with Christ for almost 2000 years; how long have your people been living with Him?" To say that it is a case of two naive/ignorant populations trying to communicate is a nice way to put it.
I'm not going to sit here on my not-even-ethnically-Coptic Coptic high horse and say that you should all feel bad about yourselves, but come on...do you really wonder why? It's the most obvious thing in the world. From the time of the robber council of Chalcedon until the 1440s at the Council of Florence, there was essentially no contact between the Coptic Orthodox Church and the West, and the contact that started in the 15th century wasn't necessarily good (that council after all did not result in reunion, and outside of the concept of Sunday School and the printing press, the Protestants brought nothing good, either). It wasn't even until HH Pope Shenouda III (r. 1971-2012) that a Coptic Orthodox Pope met with his Roman and Constantinopolitan equivalents. How can you be expected to really care about a Church that it is in the marrow of your own churches to consider as heretical? Granted, it's still better to care than to not care (for example, I certainly do care when my Assyrian friends are murdered in Iraq, even though the Church of the East is most definitely heretical; they're still people, and in some sense fellow Christians, even if we only agree on the first two councils), but the care of the Western Christians seems very fungible in a lot of cases. They 'care', but only up until we will not sit with them and say "Yes, we are all Christians! Rah rah rah!" or whatever. You would not kiss the hands of HG Bishop Abanoub of El Mokattam after he throws you all out of the church there, Westerners, and you won't like hearing that he's right to do so, because our Christianity is Orthodox (which EO won't hear either, but nobody cares; at least they are serious), and not whatever else:
Consider also that every single Western denomination outside of Roman Catholicism is so young in the context of the Egyptian Christian timeline that most Coptic people will probably not have heard of it. So the ignorance does not only go one way, either.
I know it's nice to think "Hey, we're all Christians", and like I wrote above about the Nestorians, in some sense that is true, but we're not about being Christians in "some sense". We're about being Christians in the manner given to us by our fathers St. Mark the Apostle, St. Athanasius the Apostolic, St. Bishoy, St. Shenouda the Archimandrite and his disciple St. Besa, the three Macarii, St. Theodosius, St. Theophilos, our teacher St. Dioscoros, St. Severus, St. Basil, St. Cyril, St. Gregory, St. Gregory the Armenian, and so on. If you are a Western/Greco-Roman Christian, there are probably several saints in there you recognize as saints, and several you recognize as heretics, and maybe a few you don't recognize at all. So I'm happy with the ones you know, am willing to talk about the ones you don't know, and must insist that the ones you reject are still saints, and if that means that nobody is really with us because blahblahblahblah something about St. John of Damascus and the "heresy of the Egyptians" (and I call him saint here not because he is a saint for us, but because he is a saint for the Ethiopians, even though they are our daughter church; confused? Yeah, me too...can't help you there, except to say that this is Oriental Orthodoxy, and we value our autocephaly which sometimes results in situations like this), then so be it. Again, God is our only protector. We don't
need anyone else.