Altcoins exist because too many people think with their emotions instead of logic.
Bitcoin solves a number of critical problems -- debt-based currencies with fractional reserve banking and central bank stimulus packages serve primarily to steal from the poor to give to the rich, and abuse of currencies makes socialism possible, again primarily benefitting the looters at the expense of the producers. Bitcoin can change all that and usher in a new age of prosperity, limited government, and increased personal freedom.
Altcoins serve no useful purpose. They only distract people from the real battle being waged -- Bitcoin versus Big Brother.
I like Bitcoin and believe it was something we desperately needed, otherwise I wouldn't be here. However, the sheer lack of understanding market fundamentals by "Bitcoin Only" believers is truly amazing. And yet they have the audacity to complain that altcoins aren't tanking and that altcoin adoption is illogical.
First of all, monopolies and oligopolies (be they businesses or otherwise) are quite difficult to establish and generally an antithesis to free markets. In most cases, they exist due to high barriers to entry: artificial and/or natural. They often lack the dynamic creativity and innovation seen in competitive markets. Fortunately, "Bitcoin Only" is not possible in the long run, since none of those barriers exist, thus altcoins exist and will continue to exist. They actually serve as excellent models in which innovation an experimentation can occur. Note that this does not preclude the existence of tons of copycat shitcoins, however the free market will sort those out in the long run.
Bitcoin has some serious flaws, some of which are trying to be "fixed" by papering them over with additional protocols/embeddings/centralization, but which ultimately are only going to be resolved through radical changes to the underlying fundamentals. Face it, the blockchain is inefficient and bloated, not to mention its inability to scale the number of transactions (the time is already way too long). It will only get worse as the subsidy declines and it remains to be seen if the eventual shift to mining for fees is going to work out. Without liquidity, the currency can not be used in the intended way. And then there is the whole issue of network stability and security. Cryptocurrency needs the experimentation that is happening in altcoins, because it will ultimately strengthen Bitcoin as well as provide viable alternatives if it should ever fail. Also, some of the experiments focus on using Cryptocurrency in ways not possible with Bitcoin, such as in-game currency and rewards currency.
Finally, Cryptocurrency needs people investing and holding onto it if it is to have value. However, it is very unwise to invest in one thing for obvious reasons (eggs in one basket). Investors in Cryptocurrency will want the freedom of choice and the ability to spread risk without having to engage in elaborate schemes that are basically tied to one coin. Alternatives to Bitcoin will serve this purpose.
In time, quality altcoins will establish themselves. It is not a matter of faith, but a matter of logic and reason. The only real question is if any of the current altcoins are able to fill the need. If not, then it is only a matter of time before some do appear on the scene. "Bitcoin Only" is quite untenable and unrealistic in the long run. A pity that so many Bitcoiners are so hostile to altcoins.