Altcoin important if the altcoin bring something new like litecoin ( faster transactions ), dash ( anonymous ), or ethereum ( smart contract ). If it does not add any new feature or if the feature can be easily added to bitcoin network it means the altcoin is useless.
Beyond this there is difference between a single asset and multiple choice in the market. Just think of bitcoin, it'll continue to move on its path. The existence of altcoins give the bitcoin high competence. There are altcoins that give better profitability against the profit generated out of bitcoin. It is all about the competence and the trust factor that requires the altcoins.
As stated different cryptocurrency have got varied features. Users who have got specific need can choose that one that suits their needs. Different altcoins in the market also kind of choice available for investment.
the more choices of altcoins will have a positive impact on the development of cryptocurrency, where each project will try to present their project developments well, with the various themes they raise, and of course have strategic products to facilitate human movement. However, this seems to be used for projects that are not responsible for the many frauds that occur. on the other hand there will be many speculators who get rich suddenly when they find the right project to invest in, and that in my opinion is the main attraction