why don't some company build a space shuttle to have on top of spacex heavy booster for person transport as an alternative

why don't spacex or other company build a space shuttle to have on top of spacex heavy booster to transport humans 

instead of having a spacex starship on top of spacex heavy booster when transporting people

if starship is not viable enough as person transport, then a space shuttle with the same diameter and length would negate the hypothetical problems with landing 

space shuttle was efficient at landing which is important when people are aboard