Older than software engineers, but not a lot.
Back in the days before MP3s and autotune, sound engineers had mixing desks and home stereos had dials. Turning a dial clockwise to amplify is (from an overhead POV) a left-to-right motion.
For a right-handed person with their hand in a neutral position on a mixing desk, "up", "forwards" and "right" gestures are outwards and indicate more/bigger whereas down and left would indicate less. If we were more left-handed, maybe this would have been different.
The left-right amplification motion is present in many day-to-day widgets - your car air-conditioning or your TV remote (visual display), the slider on your toaster, or maybe the reception 'bars' on your cell phone.
Also, a vast number of volume sliders do indicate that left-to-right is an increase - usually with an icon of a triangle, larger at the right.
It's hard to imagine this visual cue would be reversed in RTL languages, and I therefore don't think it should be linked too strongly with reading direction.