With Iron Fist and Luke Cage both getting cancelled in the last week or so, I've seen a lot of theories online. Some people seem to think Netflix and Marvel are ending them together since Disney is soon going to want all of its content on its streaming service, others seems to think a team-up series between the two might be coming, or maybe it was a mixture of low ratings and reviews. I'm not sure if the "popular now" row on Netflix actually means anything, but I always see Luke Cage in it, even today after its been cancelled.
If it was based on quality/ratings then Jessica Jones should probably go before Luke, since JJ season 2 was pretty awful (worse than every Marvel Netflix shows besides Iron Fist season one). It is annoying since Luke Cage and Iron Fist both ended on cliffhangers and could've had bright futures. I get the feeling that Jessica Jones won't ever top season one, which I liked a lot. I'm also hoping that this doesn't mean Daredevil will end in season 3 or even after season 4. I could see Netflix letting go and becoming less reliant on Disney and cancelling all their shows, since Disney will soon be their biggest competitor. Marvel has talked about doing Loki and Scarlet Witch shows on their service, which sounds pretty boring/lame to me, but good luck.
Update: Daredevil is now over, which doesn't shock me. I think Netflix is killing the shows since Disney is an enemy now. New seasons for Punisher and Jones were already being made.