The playback buttons are difficult to use if you have mobility issues. Their placement in the lower corner can be hard to reach, especially on iPhone. Their size is an even greater issue - it’s simply too small of a target to hit reliably if you have an impairment that interferes with normal hand function.
Most (all?) apps seem to have settled on interaction buttons at the center of the screen, which allows for greater size and spacing. I can’t think of a reason why Infuse couldn’t do similar, though I could be wrong.
At least the option for this, if not default. This could be of help for general users as well, I imagine.