If the network only clears once a minute, you need to wait at least a minute for each person ahead of you in line at the store. Alternatively, you need to be willing to pay more to cut them in line.
Equity trading only happens at a small number of venues (inclusive of OTC, dark pools, and internalizers probably not more than in the hundreds, potentially low thousands). These would be the registers. In order to buy a stock, either you choose to ‘cut the line’ by paying the price someone tells you they are willing to sell at, or you wait for someone to sell at the price you announce you’re willing to pay. These transactions are processed serially (albeit quickly) at the exchange.
Allowing trades only once a minute (or some other period) is akin to allowing the credit card network to clear once a minute. Trades cannot occur more frequently, so the ability to enter and exit positions on demand is diminished. Obviously someone who wants to trade immediately for one reason or another is harmed by having to wait. Additionally, everyone (even those not trading) is harmed by not having up to date valuations for the positions they hold.
Being closed on weekends is just fine for the market (unlike credit cards, the internet, or aircraft control systems).
Should your credit card network only allow transactions once a minute? Price data comes from transactions (trades) as they occur. There’s more utility derived from a market where people can transact on demand.
> yet the largest markets in the world are closed 2/3rd of the day
Not correct. Equity markets are far from the largest in the world, yet it’s possible to trade 24 hours a day, 5 days a week (actually thanks to HFT). Currency markets operate around the clock. Rates markets operate ~22-23 hours a day, 5 days a week.
> The fact that most markets are closed on all weekends plus over 10 holidays per year
Markets exist for their participants. Corporations looking to hedge commodities exposure, trade currencies, manage interest rate risk, or buy/sell stock have employees who work during business hours. That doesn’t diminish the need for real-time pricing. And most holidays are domestic, so major markets still operate internationally.