Often the corporations take the route of least resistance - employing dispensable workers who don't live in countries they're mapping [1], and aren't given proper training. It seems that southeast Asia (e.g. Thailand) is the major place for such dubious mapping efforts. [2]
There's also a minor conflict of authority: paid mappers (like all mappers) should defer to the community, but they have a manager who they answer to.
In my opinion not everyone has the skills to contribute, and at least if they're volunteers you can tell them (politely) to fuck off and be more likely to succeed with it (and not be outnumbered by the army of corporate drones).
On-the-ground knowledge is the OSM's gold standard. With megacorps in question routinely spending billions on frivolous stuff, they should have instead equipped the local OSM communities with gear to take 360 photos and GPS loggers to enable those on the ground to survey their local areas.
[1] https://wiki.openstreetmap.org/wiki/Armchair_mapping
[2] https://forum.openstreetmap.org/viewforum.php?id=46 (AFAIR many of people posting here are Western immigrants to Thailand, so take correction for that).