Not only because of the explanations provided by members above, but also because Telegram bots don't use end-to-end encryption between a client and a bot, making your message data stored on Telegram servers in clear text and accessible by Telegram for extraction on law enforcement requests.

Note that Secret Chats in Telegram is the only way to fully encrypt your messages without revealing their contents to the Telegram company. Moreover, Secret Chats are not available for bot communication.

Note also that Telegram collaborates closely with the law enforcement.