Yes, because they are a digital currency. You can stop calling them altcoins if you wish though and just call them cryptocurrencies instead. Maybe altcoin will go out of fashion eventually but you can't really force people to change but you can lead by example.
the thing is, they are alternative cryptocurrencies. so i think altcoin term is suitable for them.
and this is not going to change until we stop seeing new coins everyday that are scam/pump & dump/copy
Altcoins are not mature enough to be a separate thing, it needs a new feature that is actually useful and most importantly people have to accept it as a currency then it can be considered as a stand alone and be called coin not altcoin!