Well of course they need to pump and pump and pump because the dump is coming very soon More on reddit.com

Traders have to make time for hookers & blow More on reddit.com

Historically people traded on the floor of the stock exchange, so it made sense to have business hours for all of the reasons that other places have business hours -- traders went home for the night, the place needed to be cleaned, etc. Over time, practices evolved around a set trading timeline. Companies report quarterly results early morning before the market opens so that everyone can have time to understand it before trading starts for the day. Big events are generally announced at the end of the day so that people can digest it over night before the market opens the next morning. This take a bit of the competition to be the first to know info to try to beat the market and levels the playing field a bit. It also takes some of the panic buying/selling out of it and, at least theoretically, leads to fewer big swings and a smarter market. Someone can read the whole press release without trying to make an immediate decision about whether to buy/sell before everyone else does. More on reddit.com

Liquidity. Having all buyers and sellers together at one time help make sure buying and selling is easier and lowers the bid/ask spread. Look at it this way, let's say you have something collectable. Like a comic book or sports card. Where are you going to get the best price? At some convention or auction when 1000s other collectors are there....or your local shop where 3 people are there . More on reddit.com