How important are semantics when designing?

In many products semantics are overlooked and disregarded.

Forms are taken from existing products for new products thinking they will work well because they have been used before, and do not.

Also semantics are reinvented by products which sell to the masses i.e. ipod turning wheel. The generation who will grow up with the ipod will use this as a semantic reference.

These are observations I have made any further ideas or opinions will be greatly appreciated…