I can see the discussion here but i would say that altcoin help Bitcoin a lot in terms of New users being introduced to bitcoin. I also believe that altcoin are not used only for trading or so we say useful. But instead altcoin are somehow a testing grounds for some possible update to bitcoin in terms of application with regards to masses' reaction.
If we check the forum activity we can see that the most popular board is altcoins so I understand that many people were/are introduced to cryptocurrencies through these altcoins and learn more how these work and learn the power and the potential of bitcoin.
As I see it, the altcoin board is pretty popular because:
- There's a lot of spam going on in there,
- Trolls live there,
- A lot of negative trust users are there,
- Insubstantial posters are all there,
- Altcoin campaigns forces you to post there,
- and most importantly there's a lot of altcoins
Regardless, all of them are also bitcoin users although a good part of them don't post that much on other boards other than the altcoin board.