This is actually a pretty interesting question. Let me share a fun fact: in a way, the blame lies with Ethereum . The whole '7-day withdrawal lock-up' thing was first widely implemented by Ethereum and ended up becoming an industry default rule. This is because L2 transactions need a 7-day challenge period to finalize on L1. So, in the past, withdrawing from L2 required a 7-day lock-up before you could get your funds. Of course, later on, solutions like ZK and small UFO-like cross-chain bridges with prepayment made the process much faster, so you didn’t have to wait that long anymore. But a lot of projects saw Ethereum, the 'model citizen' of the blockchain world, doing it this way, and realized that delayed withdrawals could also reduce sell pressure. So, regardless of whether there’s a technical need for a challenge period, they all started copying the approach.