If everybody will use only the trusted platforms it will be impossible for new platforms to develop because nobody will use them.
Are you willing to entrust your money to individuals you do not know? or trade in an untrustworthy location?
Traders require assurance of trade security at your platform. How can we trust you if you don't ensure trade security at your platform?
So the problem is that we only find out that the platform is unsafe when hackers have hacked it and stolen our money. And as practice shows, the most popular platforms on which large sums are stored, which are so attractive to hackers, turn out to be unsafe.
Hackers are attracted by large sums. If large sums of money are not circulating on the platform, then most likely hackers will not look for its vulnerabilities and check how secure it is. And in new platforms, it remains for developers to believe that such platforms are safe. Cryptocurrencies are developing and new products are emerging that people are actively using. And if you don't try the platform, you won't know how convenient and safe it is.