Regulatory barriers differentiates them.
Utility tokens are not considered 'investments' and holders of such tokens/coins do not hold shares in the company or establishment, but can use their tokena for the utility the projects offers on its platform. Lots of projects without platforms and no utility were crowdfunding through ICOs. This created lots of distrust in the industry.

The advent of STOs would make crowd funding more seamless and would clearly define; investors and contributors. And would be in conformity will laws and regulations.