There are scammers everywhere now. Aren't they on Twitter and Facebook? Where else could they be? They are everywhere. The difference is not what we use, but how we use everything.
Scammers are everywhere, there are some on this forum as well - but Telegram as an application has features that are far more favorable for scammers than the social networks you mentioned. Besides, when someone scams you via Telegram, they can very easily delete all evidence, change their name, and look for a new victim.
Telegram is very convenient for me. In addition to communicating with colleagues, with those who also know what it is for in Telegram, aren't there many users on the forum who use the forum bot? Therefore, you need to understand that if you put a monkey behind the wheel of a car, an accident is inevitable. You don't have to be a monkey. It's simple. 
There are even alternatives to the Telegram forum bot you mention.
[SimpleX] BitcoinTalk notification bot (mentions, merits, topics, users)
[Web] BitcoinTalk notification bot (mentions and merits) - no app required