There is logic to that, especially given the dumba$$ way web content is consumed/provided. First you start with content technology--HTML5, JavaScript, Flash, Silverlight, etc.--whose foundations were that of working/hacking around structural problems with content description and delivery. Then you couple that with a plethora of implementations for consuming that content, each with their own twist on how they interpret that content.
For the provider of said content, the resources required to properly support all the variations in this environment is prohibitive. Instead, they choose a subset representing what they consider a reasonable balance between cost and coverage of users. If they were to simply let open the gates to everyone, any variation in the consumer's environment that isn't being perfectly supported will result in a bad experience for that user. This could result in any number of consequences for the content provider--technical support costs, a lost customer, a tarnished brand, etc.. Better to simple define the playground within which their customers can play, and they can support sufficiently well to ensure the consumers have a good experience.
He has not acquired a fortune; the fortune has acquired him. -- Bion