> I'd set it up very near the airport but not on it
The problem is, you need to have a good height for the antenna - "height is might" in radio, particularly above VHF bands. I actually can see this with my own ADS-B receiver - I'm in a valley and precisely can see that effect when plotting received packets.
I get good distance from my ground level antenna, but while I'm in a valley, it's very wide and long. My assumption is that most airports are going to be in fairly flat areas.
The original point was that you become reliant on a public service, probably run by volunteers, for something halfway critical to your operation. Doing it yourself is easy and then you control the reliability, not someone else.
You're just saying things that don't have basis in reality.
It's not something halfway critical to the operation–why would the FAA allow that? ADS-B Exchange is not run by volunteers–it's run by employees of JETNET LLC, an aviation intelligence company. Doing it yourself almost certainly gives you less information–you're not part of a global network of receivers. It almost certainly gives you less reliability–receivers in the big networks typically have a fair amount of overlap which gives redundancy your single receiver doesn't have.
The problem is, you need to have a good height for the antenna - "height is might" in radio, particularly above VHF bands. I actually can see this with my own ADS-B receiver - I'm in a valley and precisely can see that effect when plotting received packets.