Why is every female HM this year, apart from Steph who is long gone, a brunette??

I felt sure when they put the 3 newbies in one or two were bound to be blonde, but obviously not!!
Nothing against brunettes (my hair is dyed dark coz I love dark hair that much) but I think a blonde would've had more impact on the males, they've not seen one since Steph left and it would've been a breath of fresh air. Is there a reason for this brunette overload? Like say a twist coming somewhere along the line?? (No idea what, but it just seems very weird)