For example if you have a 6.0 or later Android, Alibaba app will block you if you disabled the permission to read IMEI or it detects spoofing.
https://postimg.org/image/m5u0nmdxd/
It is easy to see how they also use it for their own purposes: open a new taobao account, search for some items, do factory reset, install taobao and see that you are being shown same stuff you been searching before. This way they also clearly violate Google store rules that prohibit using IMEIs as tracking IDs for marketing purposes. It was reported over so many times, and Google clearly knows of this. I guess, they are afraid of antagonising "the premier Chinese dotcom" or still considering going back to China.