Manual withdrawals aren't a big problem if you don't need the money urgently. I waited 2 to 3 hours for my first withdrawal. The money arrived without any issues as USDT in Solana chain.
It's not about users having urgent need or not, it's about their comfortable experience and unnecessary meantime as well as fear of losing fund on any centralized casino by whatever reason (account freeze, fund confiscation, ...).
Of course instant withdrawals would be better.
Not actually instant but automatic withdrawal approval and processing is better than manual process.
Processing transactions manually may require manpower but it is cheap when you send everything in bulk than to be processing the transactions everytime a player made apply for withdrawal. This would require manpower and stressful for the team processing transactions every minutes as users keep applying for withdrawals.
Manually checking, approving a withdrawal request, processing it will raise many issues: time consuming, human resource consuming, but it's not worst while there is more probability of human mistakes.
It's harder to see an automatic tool that has gone through coded, tested, operated smoothly a long time has technical problems and makes mistake in processing transactions for users. It's more easily to see human mistakes which can appear anytime with any users.