Because it was all a scam and didn't need to polish details ?

One of the stranger things coming out of the collapse of FTX is that it wasn't _all_ a scam; if SBF and co they had simply let FTX function without giving special privileges to Alameda, it would have been a pretty non-scammy crypto exchange (overinflated in value, sure, but not fundamentally scamming its customers) and they all could have made great deals of money on that alone. But of course, that isn't what they did.

There have been a few valiant attempts to build crypto exchanges with modern technology and matching engines. Generally the problem these run into is that, while the algo traders and market makers love them, they have no competitive advantage in attracting retail order flow. Trading firms have no interest in just trading against each other, so without retail flow nothing happens.

Having worked on several side projects that involve money, I'll bet most money-related computer systems are full of race conditions and other wacky behavior. There are so many gotchas. For example, just writing a simple "bank account" system/database, it's tricky to ensure in a performant way that concurrent transactions don't bring a user's balance below 0. If you're sending out money via ACH or something, try handling all the ways that can fail and need to be retried.

I trade regular stocks in my Chase account. A few times, it was down for maintenance after-hours, meaning I couldn't enqueue trades to execute the next day. Not a big deal, but doesn't inspire confidence.

There’s a graveyard full of “crypto exchange but built with good tech”, ftx even bought one iirc.

The market favors move fast, market to retail, etc etc over spending time cutting microseconds off the 99th%.

A lot of the exchanges also don’t have people who know what they’re doing. Lots of normal startup folks coming from an environment where “premature optimization is the root of all evil” and “move fast break things” is the norm.