Earlier quoted context omitted.
When you're making a work of art (such as a game) you don't just want any old font, you want one that serves a particular aesthetic purpose. If you've picked a typeface, and designed other UI elements that look good in conjunction with it, but suddenly that typeface becomes unaffordable, then you have to do some work to find an alternative that's still acceptable. In particular, game UI tends to be designed around th…
Part of the reason Arial is so dominant is because it's proportioned the same as Helvetica, meaning it can be swapped in to avoid licensing fees without affecting document layout.
Arial is popular because people see it and say "good enough!".