Because no matter how super-tall-high-stratospheric your elite status is at Marriott Rewards, you don't get free breakfast at Courtyard. And the breakfast there is typically some strange "bistro" concept.

So think of it as an HGI where no matter whether HH Gold or HH Diamond you get no free breakfast, and in any case it's not the great HGI breakfast at all. (What it actually is, I'm not sure, because I've only stayed at Courtyard twice, once in San Diego when I was catching an early flight on which I was getting breakfast anyway and I was leaving the hotel before breakfast would have started there anyway, and the other time in Aguadilla in western Puerto Rico where as an MR Plat they did give me a free "continental" cold breakfast in the regular restuarant. So I've never actually seen this breakfast "bistro" which most Courtyards apparently have.)

The other difference is that the two Courtyards I stayed were easier to get "lost" in downstairs. It's like they've segmented things much more than at an HGI downstairs.