They have users. If they wanted to they could become the next Steam tomorrow by simply selling games and giving deals. The engaged userbase of discord far surpasses steam, epic, and all other gaming clients. Valve doesn't care about competing or innovating, theyll simply roll over and let it happen.

But like any startup discord is created with monopoly money and therefore they don't have any actual knowledge, expertise, or good way of gaining revenue. They're designed to spend ridiculous amounts of money to get users and sell to a megacorp. They have no ability to manage a business that requires money outside of their investors monopoly money.