There is a huge advantage to use wide array of sensors and missiles to engage intruders.
Less predictability, and wider range of required preparation ,to start with.
That's a pretty good practice for SAMs.
Not very much for AShMs (since you clog up your logistics for questionable at best differences in characteristics that might confuse the OPFOR) of the same class. *cough* Taiwan *cough*
Very bad idea for aircraft, since the maintenance headaches (fighter jets are a lot more attention demanding than a bunch of SAMs and radars on trucks) *cough* Egypt *cough* India *cough*