Today almost all people have smartphones.
A smartphone is the main device with which a person spends most of the time during the day.
The main mobile application on any smartphone that every person uses every day is messenger.
There are Facebook Messenger, WhatsApp, Viber, Skype, Telegram and many others.
In 2017, only one messenger, from Facebook, developed the best tools for creating chatbots on its platform.
Chatbots for other messengers do not have such powerful features that are available in Facebook Messenger.
Chatbots do not require downloading and installing on a smartphone, do not take up space in the phone's memory, and they are also available on desktops and in any browsers.