Because of the price of real estate in NYC, any space at street level is valuable and cpuld be used for any kind of bar, restaurant or retail store. I'm not making excuses, because I come accross a lot of narrow minded music presenters in NYC, but the reality is if you want to hear adventurous music, and that may be any kind of jazz soon, you will have to find it in the places like Clem says and in the smaller, 2nd and 3rd storey rooms.
I mean, I'm not a big fan of Iridium, but at that location in Times Square, they could put in almost anything and make more money. To their credit, they have been adding late night sets ( 3rd sets) with new and different talent lately.
All accross the country there are clubs who off the split mentioned in the article. The real problem ( except in the largest cities) is that they won't give you a weekend, but want to do this on Wed. & Thurs. Forget the weekend, they can hire anybody to fill the place on the weekend.
To have a career in this music you have to do it all: selective workshops & clinics, publishing, recording ( both as a leader and sideman), non USA tours and clubdates, festivals, on site cd sales and yes, NYC club/concert dates.
Because to many, if you don't play NYC as a leader, you aren't one.