if you think the only thing of bitcoin is to buy/sell it on an exchange. thats your error.
people can mine it, and work for it. and sell and buy goods and services for it

heck there are people on this forum getting paid in bitcoin to moderate this forum and well the obvious ones that spend their time advertising businesses and altnets.

so imagine a world without a btc-fiat exchange.. bitcoin still has function.
miners give it to employees as a wage, merchants sell goods and produce for it. and pays their employees. the employees then buy goods and services with it... oh wait thats called a currency.. wow i just described bitcoin as being a currency.. amazing.. right..

bitcoin is more then an investment its a currency. before bitcoin even had a exchange market price. people were buying pizza, alpaca socks, cupcakes and even drugs with it.
wiki was accepting donations. the list goes on. all before things like mtgox really got established.

even before that bitcoin was used for multiple things. you would be surprised what you can do with bitcoin.

even as a investment. there is more then you can do with it then just holding value. you can organise that value without the need of bank managers and lawyers. by this i mean things like multisig to put it into escrows, or family trusts or off shore storage.

but hey. if you think that if the exchanges disappear bitcoin has no features.. you have a big lesson to learn.
face to face swaps were even a thing before exchanges. so that will continue too