How come Huawei watches don't even have calculators on Apple phones?

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. At present, there are almost 30 applications that support downloading, such as ink weather, calculator, perpetual calendar, Gaode Baidu map, Didi Chuxing, etc. QQ and WeChat are not available for the time being, and it is estimated that they will increase in the future.