Because the Jaguars are not meant to engage the enemy for A2A clash, rather the ground strike mission and for that role we have lot of choices such as MKI, Mig 29 UPG, Mirrage 2000 UPG. For the BVR operation, you need long range Radar operating in a2a mode, and if you switch to such mode the jaguar will reveal its position, which is not intented, rather the Low altitude, terrain following, terrain masking deep strike strike operation. The AESA Radar, is meant to do the SAR scanning and mapping, and terrain following, terrain avoidance look down mode operation.