Why can only 70 words be entered in a short message?

This is not the regulation of the operator, but the regulation of the underlying communication protocol. All mobile phones must abide by the same communication protocol to ensure that the sent short messages can be correctly forwarded by the mobile operator's server, and also ensure that the sent short messages can be received by another mobile phone and viewed correctly. Some mobile phones can send long messages of more than 70 Chinese characters, but in fact you think your personal editor can write so much. When sending, the mobile phone is automatically split into multiple short messages according to the standard of 70 Chinese characters per short message, which does not mean that the mobile phone has broken through the protocol limit of 70 Chinese characters per short message.