There are very pertinent and valid reasons for that. While it is being touted as a multirole aircraft (and it is a multirole aircraft) the primary focus of the JF 17 is air defence. Therefore all focus in developing tactics, weapons and even the logistics has been focused on air defence employment. That does not mean that the aircraft is/has not been cleared for accused in air to ground scenarios; rather that the focus of the aircraft is 70% in air defence for the time being. This is also evident in the the commonplace sight of the aircraft practising Air combat scenario's much more frequently as compared to air to ground. At this time(barring the F-16) the JF-17 is the only platform the PAF has which provides complete air combat capability in both the BVR(publicly known that is) and WVR arena and was built for that purpose. Hence, with the F-16 fleet working up it is also imperative that the Air Defence capability of the PAF is kept sharp throughout the timeline the aircraft is coming.
At this point, the rather lacklustre marketing effort is the fault of the PAF and the Chinese as well. The PAF wants to ensure that its JF-17 orders are met before anyone else gets them and the Chinese are trying to sell it like their next F-7. The PAF has firm orders for 150 and is now debating in light of the IAF's purchases whether to push it all the way to 300. Within that, there is pressure to fit in foreign orders but the PAF is adamant that it wants its orders and before anybody else. Let's be clear, that the only assembly-line (able to manufacture JF 17s on a large-scale) is in Kamra, Pakistan. The Chinese or rather CATIC has no room for a JF-17 line as they are currently absorbed with other projects. The slow rate initial production was due to this specific reason that the complex in Kamra was working up and till then JF-17s were built on a single jig in China.