It's simple. Speed and cost. Python/Ruby projects cost less fixed cost to develop and maintain. They cost more to run and scale. Startups lack development and

It's simple. Speed and cost. Python/Ruby projects cost less fixed cost to develop and maintain. They cost more to run and scale. Startups lack development and maintenance costs and generally scaling dollars are followed by revenue or additional funding to finance that cost. -- Additionally Python/Ruby have a lot more features, frameworks, extensions that specially deal with modern startup issues.