Even if the tokens created for internal perposes they must be listed at the ecxhangers. Investors must have an opportunity to buy and sell tokens anytime they want.
There are still very few utility tokens in crypto. Most assets are purely speculative. Therefore, to ensure liquidity, listing on external exchanges is necessary.
Acording whitepapers of ICO nearly all the tokens are utility but the matter is that tokens are not realy used on the platfroms or platforms do not ready. That is why the tokens are speculation becouse they do not have any more use.