At that event, Nothing Technology's Steven Gao asked a question to participants about importance of IP68 resistance in Japan. The answer was like this: Many people use iPhone to take pictures, and that dust and waterproofing is important because smartphones are part of our body.
After the event end, I told my viewpoint of importance of IP68 resistance in Japan with weather conditions to Steven Gao. This time, let me reorganize and explain my thoughts. In my viewpoint, there's another different reason.
Why IP68 resistance smartphones are wanted in Japan?
Briefly to say, because we are living in Japan.
Generally speaking, in Japan, from June to July is rainy season called Tsuyu(梅雨). Perhaps it's different as wet season and dry season in Africa. From July to October is the time of year when Typhoons(台風) approaches Japan the most.
So, these rainy weather in Japan makes demand of IP68 or IPX8 water resistance smartphones, especially IPX8 water resistance smartphones are wanted in Japan. To get the peace of mind of being able to use smartphones in the rain.
Personally, IPX7 water resistance smartphones would suffice for me, RuinDig, this blog article author.
Reference articles for IP68 or IPX8 water resistance rating