But... But I was told non-mining nodes are essential to Bitcoin security and decentralizationings

And I when I told you that non-mining nodes are irrelevant, because trivially faked, you got upset...
And now
...you're telling me that non-mining nodes are irrelevant, because trivially faked?

Non-mining nodes
are essential to security and decentralization. That doesn't mean that we have good (or complete) information about node counts. The former is a statement about how miners' selfish interests are balanced.
All the
non-mining nodes wallets currently running could be replicated within ... I'll let your buddy answer
That's a lot harder to argue. I said data on nodes is incomplete -- not altogether useless. Operating a node means expending resources on bandwidth, storage -- those have costs. That's why the key to this data is in short term vs. long term analysis.
It would be astronomically more expensive to operate 5000-8000 Core nodes over the past two years than it would be to spin up 800 Classic nodes over the past week. That the data is not completely transparent does not mean we should ignore it entirely.
Lol, how much, would you say, as compared to running a major factory mine? 1/100000th as much? Less?
If you invest a million dollars into mining BTC, might you not throw a buck or two @ nodes?
Heck, Bitcoin wiki tells me somebody was *incentivizing nodes* 'til recently:
Some are incentivizing it
Bitnodes is incentivizing full node operators "until the end of 2015 or until 10,000 nodes are running."[2] For rules and how to join the incentives program, visit Bitnodes Incentive Program.
Anyhow, doesn't matter how long the "bad" nodes stay up, if they're meaningful to Bitcoin security in any way (beyond being a good wallet), a few hours is just fine.