Why not? Don't you want to stop all the crimes happening in bathrooms too? That would be a logical step if privacy is always an acceptable tradeoff for security (or at least the illusion thereof).

The difference is that public streets are public spaces. You necessarily have a limited expectation of privacy in public spaces. The government likewise already deploys cameras in public places to maintain a reasonable level of order on them.

If you want to put a camera in your personal toilet you absolutely can.