An alternative is needed, it is safe. On the other hand, how would exchange trading work if it were not for altcoin?
That is right, it is not that bad to trade other digital currencies besides bitcoin, also imagine trading only bitcoin in exchanges, do you think it will be a good trade? Just trading BTC to USD and vice versa, that is pretty boring and I don't think that will attract more traders or investors. Also, not all people are that kind of attracted to bitcoin, some of them are also attracted to some alternative coins just like Ethereum and XRM.
Forgot the speculative side, because it's not the primary purpose to create a coin. Focus on the basic advantages we get. I am a strong Bitcoin believer but I also think some altcoins are needed. The coins focused on privacy such as Monero, Zencash, Cloackcoin, etc. It helps where Bitcoin is not good at, and believe it or not the anon coins will be a lot of more soon.
Indeed, we should be diversified some.
Bitcoin solid value.
ETH smart contract thingies
LTC speedy cheap transactions
DASH speedy cheap and also widely used
ZEC, XMR, good privacy coins.
Got some them all! 2018 will usher in a whole new era for the crypto..IMHO