The reason they are not inducting JF-17 is because it is only marginally better than J-7. JF-17 is evolution of J-7 program (The 7 in its name come from there) , and has been called by most experts as newest version of Mig-21 (Like here:
https://warisboring.com/this-is-the-ultimate-mig-21-715bb9297261#.oj80auu4w ,
http://www.military-today.com/aircraft/jf17_thunder.htm ,
http://www.airvectors.net/avmig21_2.html ). This is like India inducting Mig-21 Bison as its next generation aircraft.
The thing is that Chinese have stuck Pakistan with a lemon. JF-17 would have been OK has it been in its mid-life or fighting Indian Mig-21s, but they would be flying for next two and a half decades at least. I cannot help but lol when Pakistanis innocently ask "Why their airforce is in love with F-16s?" or "Why PAF is buying F-16 when JF-17 is better than F-16s?". Little they know that even early F-16 models are superior to JF-17, that's why PAF prefer second hand F-16s over JF-17.
This is a very weak excuse when 2/3 of your airforce is flying junk (various iterations of Mig-21s with even some Mig-17s in service). The reason why China is not inducting JF-17 is because it is a reworked J-7, and they are not willing to be struck with a Mig-21 variant with a third gen stable airframe for next 30 years.
If you skeptical, check links that I have provided in previous post. Most expert consider JF-17 just an improved version of J-7, which is a copy of Mig-21.