Pretty much every named character of any notability, in both TV trek and the movies, comes from the homeworld of their species. Any human will come from Earth. Any Klingon will come from Qo'noS. Any Vulcan will come from Vulcan. Any Cardassian will come from Cardassia. And so on. By the TNG-DS9 era in the late 24th century, humans have been a star-faring species for over 300 years. Look at how fast North America was opened up with European settlement... By the time of TNG/DS9, the older human colony worlds, like Vega Colony, Alpha Centauri etc. should already boast human populations of hundreds of millions, if not billions. There should be humans out there who have never set foot on Earth, but all we ever get are people born and bred on Earth. It's silly.