Because it's a dumb thing to be doing.
You probably don't realise that many aircraft don't have ADSB-out and your app won't be warning you about them.
And the planes that don't have ADSB are mostly smaller planes which are the ones most likely...
"I'd have to be real careful crossing the runway"
Why would you fly anywhere near a runway of even a small airport? At least it will let you takeoff, then fly away from the airport. Anything else is just irresponsible.
Yes it's understandable but frustrating that DVR free won't do 10 bit. But DaVinci Resolve full version is actually priced very reasonably, and in a world increasingly heading in the direction of subs-only it remains rare that they are not doing...