Already this might have discussed. The growth of bitcoin as well other digital currencies keeps progressing with time. By the time common people too have begun to use cryptocurrencies on their daily life. Compared to the fiat usage, common people using cryptocurrencies were low. When the usage increases what will be the preference of common people. Whether it gets used as investment, gambling asset, trading asset, alternate payment, darkweb usage source.
Your title says one thing but your post asks another question.
Anyways, answering to your title, the usage of bitcoin can be increase through mass adoption of crypto currencies. To do that we will need to spread the knowledge of bitcoin around the world.
To answer your post, it will be used more as an investment. Even online crypto gambling casinos will also increase, no doubt!