In all fairness—npm belongs to GitHub, which belongs to Microsoft. Amateur-hour is both not a valid excuse anymore, and also a boring explanation. GitHub is going to great lengths to enable SLSA attestations for secure tool chains; there must be systemic issues in the JS ecosystem that make an implementation of proper attestations infeasible right now, everything else wouldn't really make sense.
So if we're discussing anything here, why not what this reason is, instead of everyone praising their favourite package registry?