Priority. Concentrate on the critical points to the Turkish boarder where most Rebels are. Contain the small pockets where the rebels can not do much other than survival. SAA is limited in manpower, this strategy is the only choice. If Syria does the opposite, there is a big chance the north will be lost to the Turkish backed rebels, essentially partitioning Syria, making Syrian government a regional faction than a national government, less legitimacy to stay in power, giving the anti-Assad factions more excuses to invade and topple. This also explains why SAA stays out of the fight between IS and Kurds to the north east. I would do the same thing because neither Kurds nor IS can ever gain legitimacy no matter how big area they control, none of them can gain a collective support from all major players. But the so-called "moderate" rebels are totally another beast, they are proxies, they will gain "legitimacy" if they hold a big chunk of land and population.
SAA is in a race with time, it must cut off or contain of finish (unlikely) the rebels to the north before Turkey can establish a strong foot hold in the north-east.
