Why does the Huawei watch not have a calculator when connected to an Apple phone?

Huawei watch3 has a calculator. After the watch is connected to the mobile phone, you can use the watch to download other applications in the watch. Currently, the supported applications include Moji Weather, Calculator, Perpetual Calendar, Amap Baidu Map, Didi Chuxing, etc. There are almost thirty applications, QQ and WeChat. Not yet, but it is estimated that there will be more in the future.