A purpose other than "my boss wants his name on a language." Once you identify a specific type of problem that is not solved by today's programming langauges,

A purpose other than "my boss wants his name on a language." Once you identify a specific type of problem that is not solved by today's programming langauges, you have the basis to go create a new language. Maybe you find that it's hard to express some AI concept, or complex math, or to make easy web applications---each of those needs led to very good programming langauges. Otherwise you're just adding language clutter, re-inventing the wheel, and wasting a lot of time.