That's the ridiculous part about the old economy - it's not 24/7. How can you have a non-24/7 in a globalized, bot-controlled financial market? Makes no sense to me.
There
is off-hours trading, so some traditional markets run 24/7. Forex runs 24/7. But it's true that in traditional markets like stocks and most commodities, you need to account for gaps. Lots of day traders close positions at the end of the week to avoid weekend shenanigans and surprise Monday spikes.
Forex markets do close for the weekend so they are 24/5 generally. The NYSE has
extended hours pre-market trading 4:00 a.m. to 9:30 a.m. and post-market trading from 4:00 p.m. to 8:00 p.m. Then there are also futures markets, eg. CME S&P 500 futures only close for 1hr so trade 23/5.
I don't really think this actually makes any difference other than the psychological effect of gaps that occur when a market reopens after a close period are absent from crypto markets.