For what it's worth, not having a cell phone number is really annoying.

Sichuan Airlines (https://www.sichuanair.com/) only lets you book a flight when logged in, and phone number is the only method of logging in.
Air China (http://www.airchina.com.cn/) lets you login with an email BUT creating an account is impossible unless you send a text message to 95583 to obtain a captcha for your mobile phone.

Back to Trip.com/Ctrip I guess...