As I understand it, a rocket should produce its maximum thrust on liftoff. As time progresses, the mass of the rocket will decrease, but since the engines produce the same thrust, the rocket will accelerate faster. So, all rocket engines on the first stage (which aren't blocked by other stages) should ignite on lift off, which will reduce the mass of the vehicle quicker, giving more acceleration. This seems true for most rockets.
The GSLV MK3 ignites its core liquid engines (L110) approximately 120 seconds after liftoff. As described on the launch video, the exact timing depends on RTC (Real Time Decision). This requires the S200 Solid strapons to lift the full L110 mass for up to 120 seconds.
What factors dictate this kind of staging sequence? Why are the L110s not ignited on liftoff? Is max Q the reason?