This is, of course, a personal decision. For some, even the most inexpensive Apple Watch can be a major investment, well worth protecting. For others, the idea of damaging their watch's hardy Ion-X glass may be unlikely enough, or inconsequential enough that they would prefer to just take the risk and pay for repairs, if needed. Ultimately, it's a matter of budgeting for the cost of potential future repairs versus the definite cost and possible aesthetic blow resulting from adding some form of screen protector.