Your substitution would hold up if we didn't need a lot of folks mining.  You don't need a lot of people mining gold in order for gold to have value.  But we do need a lot of people "mining" BTC in order for BTC to have value.  If the blockchain doesn't get built, BTC has no value.  So what's going to happen when their are only a few people building the blockchain?  If only a few people are generating BTCs isn't that a problem?

You might respond, "If only a few people are mining gold, that's not a problem, because gold will still have value."  But that response doesn't work.  Gold will continue to have value whether or not anybody mines it.  (Why?  Who cares.)  BTCs will have NO value unless the blockchain is stably built.  The value of BTC requires their being a lot of "mining" (I use "mining" as shorthand for "helping build the blockchain").  When the vast majority of miners get cut out of business, what's going to happen to BTC?