Is there a reason why Greater Invisibility is …

Is there a reason why Greater Invisibility is a separate spell?

If I recall correctly, we wanted to avoid spells where higher level spell slots had different effects among themselves. With invisibility, level 2 gives 2 targets, 3 gives 3 targets, etc. Hard to allow that and improved at some point. — Mike Mearls (@mikemearls) February 10, 2018