I'm not saying it's bad, I'm saying that you can still have races and thus still need some form of synchronization even when using async/await. Whilst in simple cases you can preserve invariants just by carefully choosing where an await is done, as things get more complex you constantly run the risk that someone will introduce another await somewhere else (and maybe more async marked functions to enable that), without understanding that the 'await' can now run code that violates some invariants. Locks and other such mechanisms let you mark certain code as executing atomically regardless of scheduling.