If that were true, we'd have a one world currency by now. But at least the last time I checked, there's the US Dollar, the Canadian Dollar, the Euro, the Australian Dollar, the New Zealand Dollar, the British Pound, etc.
Discussion
The question was what makes Monero a weak store of value. What you’ve listed are currencies, which are also weak stores of value—by design. Currency issuers compete to weaken their currencies to boost their numbers (exports, GDP etc.)
Right, but you said that money was a winner take all proposition which has never occurred throughout history and is very unlikely to occur now as people have different opinions on what money should be. You can absolutely have a dominant currency, but I don't think you will have only one currency. Bitcoin may be the first, but I do not think it will be the only.
Fair enough, moneyness is continuously reinvented by people.
It is simply too easy to create shitcoins, and the motivation to print one’s own money too strong to imagine that we’ll ever be totally rid of them. There will be a long tail of shitcoins and their promoters, forever.
All of them suffer lack of first-mover advantage to Bitcoin.
Which is why I do not play with those but some coins such as Monero actually have a legit proposition and for Monero it's digital cash and as much privacy as can possibly be granted in the age of a computer.
Money is the most saleable good. Neither Bitcoin nor Monero meet that definition.
Money is also fungible and private like gold and Monero. Bitcoin doesn't meet that criteria either. So it is not so clear what it is.
Bitcoin also had first mover advantage in DNMs, it's first use case, but is being phased out by Monero.
Monero is p2p digital cash. It never claims to be money.
Bitcoiners claims that Bitcoin is money, but that becomes dubious on any simple inspection. It is treated as a digital commodity by most.


“Is” arguments are among the most vociferous and yet inconsequential. What “is” money, etc.
The question was why do Bitcoiners consider Monero to be a poor store of value. My answer remains that as a shitcoin, of which there are and will be countless, Monero lacks and cannot gain first mover advantage against Bitcoin.
Your first mover advantage claim has already been disproven with one major example; DNMs. There are also various other white market examples like Coincards, ShopinBit, SilentLink, etc where that is clearly being shown as untrue.
First mover is helpful, but is not some immutable law and guarantees nothing. Ask Myspace, Blockbuster, Sears, Kodak, cassette tapes, CDs, and countless other defunct technologies and brands about first mover advantage. You stagnate you get left behind. The market doesn't care if you were first and currently the most popular.