The issue of dropping Watch with increased weight is a problem.
Dropping an aluminum with ion-x(more shatter proof than sapphire)has a good survival rate.
Yes,expensive watches use sapphire,but most are extremely water proof and have crystals up to 4mm thick to deal with water pressure,not so with Apple Watch.
There are no waterproof watches. There are only water resistant ratings. That's regulated by the Federal Trade Commission.