We should probably quantify "long", I know it's been a few years at least because I added a couple of businesses myself. But I guess it's already been well over 6 years since Apple Maps' initial launch (how time flies!), and there have been plenty of changes since then, so you could well argue even a few years isn't that long in the scale of the thing. And the 1.0 launch sure was rough a heck, not many such things where there has to be a public apology given let alone from Apple. Some of their initial ideas for how it would develop (with heavy 3rd party dev involvement for example) never really seemed to work out, and they've become more, "traditional" I guess over time in terms of data sources and doing the grunt work themselves (IIRC they started doing their own sensor vans for example like in 2015/2016?). At any rate though it's there now and has been for a bit, it's in the Mac version as well and I can see it even in older ones.
Having said all that, I just checked some of the entries I made way back when, which I did with full write ups, my source, photos, and in one case I was in fact the business head of IT and provided that from my work email and a device on our business Apple ID even. And I'm positive those were accepted and on the map for at least 6 months while I was still there. Yet now I look and nothing, and they definitely are still in business at the same location. That's kind of a crappy. If Apple accepts user submissions but then blows them away from time to time during map source fusion say it could explain some of their paucity of data and would discourage more submissions from those few who bothered in the first place.