There are whole books on this, but the short summary is that there are infinite times when information can change that would affect the value of a company. Anything less than infinite trading is a compromise where the price is no longer reflective of the value. The bigger the gap in the time, the bigger the gap between price and value.

For example, if you could only trade once a day, let's say a company announces midday that some huge customer has just left their platform. Their price should drop, but without trading it can't. So now everyone knows that their value is lower, but can't do anything about it. So people who own that stock will hold their money and not make other trades, because they know they are going to lose a bunch when trading happens again.

> The very existence of holiday weekends shows that it's actually totally fine if you go 72 hours without any trades resolving.

Trading never stops. There is an entire secondary market that has after hours/weekend trading, and a tertiary private market when that one isn't open. It's just you (and all the other retail traders) who can't trade.

Which if anything proves the opposite of your point. Liquidity is so important that wealthy people set up an entire system to keep trading just so they can still have it.