Why isn't the frequency dependency of an Operational Amplifier not considered
Shouldn't the transfer function of OPAMP's internal circuitry be
  considered for accurate analysis?


For DC (low frequencies) it is unlikely because, most engineers know that the open loop gain of the op-amp they will be familiar with is around 100 dB or greater. This is a gain of 100,000 and for 1V on the output, you need an input differential of 10 uV. This is usually far in excess of the input offset voltage error hence for DC (low frequencies) nobody really cares about the transfer function.

However, if you have to make a DC accurate amplifier with a gain of 1000 up to 20 kHz (flat to +/- 0.1 dB) then you get stuck into the data sheets to see what the open loop response looks like. Or you just use the gain bandwidth product value to give you a reasonable idea.

Or just start simulating in PSpice (or equivalent). However you still need to exercise care when using sims.