That's exactly why what we need is a common framework such that when every person and company does make their own cryptocurrency, the exchanges can handle settlement and barter-matchmaking in a seamless and mostly automated fashion.
So if Kodak has a standing offer to register stock photos and do rights clearance and licensing forever for X Eastmans, and I have a standing offer to exchange software development services for Y Blammos per day, the computing power that people offer in exchange for Hypotheticoins cranks through an arcane and unspecified algorithm, then spits out a result where I get what I want, and I have to do some work for an ex-dental-hygienist that once worked for my dentist. And I also get some change for it. For doing the job, I not only get the Kodak service, but I also get a medium 2-topping pizza from the nearest Domino's, an oil change and brake inspection from my regular mechanic, and 3 weeks of lawn-mowing from a kid on the next block.
To my knowledge, Bitcoin can't do this, and an assortment of fragmented unitasker coins can't do it without an array of attached service businesses like Coinbase and BitPay.
I'm really keen on a future where cryptocurrency enables a gift-barter economy, where you can make wishes, and grant other people's wishes. The more you grant to others, the more you get in return. I think that's a kind of thing that most people can really support, but it hasn't happened already, because the administrative overhead is a nightmare. With human matchmakers in the loop, you can only reasonably handle big wishes, and so you can't pay people back for helping to grant them. And so the recipients are kids with terminal cancer or rescued animals or something, so the givers get paid with warm fuzzies, or a kind of pay-it-forward IOU that might possibly go all the way around the world and come back. With an automated and distributed system cranking away on it, you can get that jar of homemade pickles for calling up a complete stranger to wish them happy birthday, or get a free beer for reciting one line at the right time in someone's bizarre public performance art. Or maybe you can finally get that pothole filled in front of your house, and all you have to do is reduce 300 MB of traffic survey data to determine the 85th percentile of traffic speeds.
You can't stop everyone from making their own coins. Might as well try to make them all work together.