Right? This is what I've been saying for a while about this franchise.
The author made the other three houses almost non existent compared to Gryffindor.
I've been thinking...instead of making Hermione (or Luna,for example)...from Gryffindor, I prefer her to be either from Ravenclaw or Huttlepuff. And don't make all of Slytherin students looks like the "hahahaha" ultimate bad guys all the time. It would make the dynamic even more interesting,imo...if there is one slytherin student in Harry's circle, instead making all of them comes from Gryffindor.
It is like in Super Sentai/Power Rangers..if all the 5 members/rangers are all sharing the same trait as the red, for example...it would be incredibly boring with no diversity in characterization.
But it is what it is...and this is why I don't really regard this franchise as highly as others.