- It removes the risk of spending time and money learning what turns out to be the "wrong" (i.e. an unsuccessful) platform

- It avoids splitting the effort of tooling vendors, library authors, etc. across many different platforms, reducing the amount of redundant effort spent reimplementing things in platform Y that already exist in platform X and freeing them up to work on unique ideas instead

- It brings the largest possible number of people underneath one umbrella, which makes that community more economically attractive and therefore increases the number and quality of tools and services they have access to

Not that it's all sunshine and roses, of course, but it's not without advantages.