because like a system where every alt has its own class.. you have a main and that main gets special treatment.. now you can level 1 job in coil, 1 job with myths and a 3rd job with CT.. not really sure what else you want, if you could do it the way you want, you would have all jobs fully geared in CT gear in 5 weeks.. but you dont get another CT update for 6 months, then what? spend that extra time complaining on forums about the lack of content