This is in no way 'a weak argument'. Trustlessness is central to Bitcoin's USP. For everything else, there is Visa.
No it's not. If it were then people won't be holding their coins in centralized exchanges:
https://blockchain.info/charts/my-wallet-n-usersAnd Coinbase and the rest of them.
Here you argue against yourself. You argue that nodes not being incentivized is a fatal flaw. I point out that implementing a full node is relatively negligible for anyone who already owns a computer and an internet connection. Your rebuttal is that third-worlders only make $2/day? Such a economic citizen is unable to overcome this financial barrier no matter the incentive to run a node.
It would be trivial, but people still don't do it, because they don't care.
Out of the millions of BTC users, only 5-6000 are running nodes. What does that tell you?
It looks to me that less than 0.06% of the users care about trustlesness, if we assume a conservative user estimate of 10m.
Which reinforces my hypothesis that I have told earlier that:
Look, nobody cares about trustlessness, other than the VIP bitcoiners who have upwards of 10,000BTC.