As others have explained, there is no security provided to the network by non-mining full nodes.
Mining and "full nodes" are two different things.
Mining =
https://shop.bitmain.com/ or
https://canaan.io/Full node =
https://bitcoin.org/en/download or
https://www.bitcoinunlimited.info/downloadMany who mine run full nodes. One solves the puzzle and the other holds a copy of the blockchain. Both are security, but in different ways.
EDIT: If people want to be paid for running a full node, there is a coin for that:
DASH.
Bunch of worthless shitcoin miners or unemployed masses who hold thousands of worthless mining equipment in their garage. And one day, one of y'all BU supporters gonna say fuck it i'm going with SegWit.
Maybe. Or going from shitcoin to shitcoin and finding the best exchange into BTC, LTC or USD. It'd take monitoring of the markets daily.