Apple did not make the Apple Watch waterproof because it was not a necessary or desirable feature for the device at the time of its release.
The Apple Watch is water-resistant, which means that it can withstand splashes of water and brief immersion in water, but it is not designed to be submerged in water for extended periods of time.
This level of water resistance is suitable for many everyday activities, such as washing your hands or wearing the watch in the rain. However, it is not suitable for activities like swimming or diving.
Making the Apple Watch waterproof would have required significant changes to the design and construction of the watch, which could have increased the cost and complexity of the device.
Additionally, waterproofing the watch would not necessarily provide any significant benefits to most users. For these reasons, Apple decided not to make the Apple Watch waterproof.
However, subsequent versions of the Apple Watch have improved water resistance, with some models being rated as water-resistant to 50 meters, which is suitable for swimming and other water activities.