Having them checked at runtime is still important (I say this as someone who was involved in scalar types getting declarations finally), because it means that t

Having them checked at runtime is still important (I say this as someone who was involved in scalar types getting declarations finally), because it means that the types can't end up inaccurate without being noticed, weak typing can be supported with certainty (you always get the type you ask for), and as a bonus the runtime can perform optimisations (elided type checks).