Why is the number of Long Gamma Ray Burst (LGRB) event occurrences greater than the number of Short Gamma Ray Burst (SGRB) event occurrences? I collected  from NASA this histogram plotting the number of GRBs vs the duration of GRBs.

Now my question is, why is the number of Long Gamma Ray Bursts (LGRBs) events occurrences greater than the number of Short Gamma Ray Bursts (SGRBs) event occurences, since on that plot the area covered by the long duration GRBs is greater than short duration GRBs?
Long and short GRBs are thought to arise from different types of event, involving different types of star. Therefore the question you should be asking is why are their event rates so similar?!
Long duration bursts are thought to be produced in the death throes of rapidly, rotating massive stars - the hypernova model. Short GRBs are thought to be produced during kilonova explosions, after the merger of two orbiting binary neutron stars. Short GRBs are less luminous than long GRBs, but they are also systematically closer, and so their observed gamma ray fluxes and hence detectability are similar.
However, these are quite different things, so there is no reason that they should share similar event rates.