Idiots
I am currently connected to Ye InterTubes thanks to a connection at an IHOP (their coffee is both better and cheaper than Starbucks, not a high bar, and the pancakes at this location are pretty good; some IHOPs and every single Denny’s that I've tried manage to do the impossible and fuck up pancakes, so this is not a given,) while using a VPN. A check without the VPN says my IP is in Miami; I am nearly 100 miles away. IHOP seems to have centralized its internet connections. With the VPN, I'm in Kansas. I'm really in Florida. It's trivial to screw with those wanting to see your IP. You know VPNs have gone mainstream when a VPN company (Nord, not the guys I use) runs ads on the Super Bowl broadcast. And they say straight up that they would prevent others from seeing your actual location. Free VPN-like things are built into Apple OSes and available from CloudFlare and others. As far as I know, Apple’s stuff is turned on by default, while it's trivial to set up CloudFlare. Free VPNs tend to be limited; if you need more control, pay up. I suspect that Microsoft and Google have something like Apple’s stuff, but I trust them even less than I trust Apple, and I can't be arsed to go look. There would be a reason why I use a 3rd party VPN…
Not to mention that if you use institutional internet, your IP will be that of the institution. A large college-level institution here in Deepest South Florida might have tens of thousands of users; Miami-Dade College is the largest tertiary-level institution in the US, with 170,000 plus students. Broward College has maybe 50,000, and Palm Beach State has over 60,000. A lot of housing developments and condo associations have deals with various IDPs, so everyone who lives there will be coming from a limited set of IPs. There will be a lot of duplicate hits. Lots of people will be hiding their IPs. Getting the IPs of those who clicked on ads would not necessarily generate the data the admongers want.
This is, of course, over and above any privacy questions. If the admongers did force Reddit to cough up the IPs, it would be difficult to do as the admongers aren't cops and will have difficulty getting court orders; furthermore, they are setting themselves up for massive class-action lawsuits—lots of them. Be careful what you ask for; you might get it.