Securing an S3 bucket with proper permissions, encryption, and bucket policy is not necessarily rocket science. The tools are all there, but tell someone who doesn’t care about security to set up an S3 bucket for your company and the end result will likely reflect that. While AWS has plenty of faults worth discussing, this specific issue is not on Amazon.
But it does sustain a cottage industry of consultants that either sell the work of configuring it, or second-order grifters that just sell the "know-how".