Relaying blocks is not a big deal. Your argument is not qualified enough to be discussed here, sorry, blocks get relayed anyway, e.g by collided pools.
I don't see how this part of your post is right. That is simply wrong, and I doubt you truly understand how the Bitcoin network works.
Blocks are relayed to any client, being a mining full node, a full node wallet, an SPV wallet, a blockchain explorer, ...) who connect to a pool/solo-miner and/
or any full node that accepts inbound connections. What do you mean by accusing me of being ignorant about bitcoin relay network? It is not so complicated and I've been discussing it on many occasions in this forum.
Because they are ONLY connected to a full node, that validates, the clients that ONLY connect to the full node DON'T DO anything for the network, and are NOT truly part of the network.
Plus, full nodes are not able to detect mal-incentivized reorgs and censorship the most practical threats due to mining centralization.
Then why haven't they tried it?
You guess! It is not a rational move, simple
game theory.
In the network's current form, Game Theory, because?
How? Let's dive in:
There is a very efficient, secure way of running a bitcoin full node on commodity mobile devices very efficiently in economic mode, called UTXO commitment. According to this model miners would have to commit to the UTXO (state of the bitcoin machine) by somehow including its hash in their blocks and a light full-node could besides synchronizing headers like a usual SPV wallet continue to downloading the full state of the machine as of latest couples of hundreds of blocks and act like an ordinary pruned full node thereafter. Right?
If "that" doesn't validate and relay transactions/blocks, then it's not doing anything for the network, and therefore not part of the network.
"That" is an ordinary bitcoin pruned full node and does everything an ordinary full node can do other than uploading the ancient history of blockchain for the current (stupid) bootstrap process.
Listen, if it's not validating, and relaying blocks. It's not part of the network.