Would you expect to observe every supernova in our own Galaxy? Why or why not?

Only few supernova are observed in our galaxy -

Type II supernovae (i. e. the explosions of the massive stars) occurred in the Milky Way, and they might be hidden by the intervening dust if they are located in the more distant parts of our Galaxy.

Type Ia supernovae, which need a white dwarf star in the binary star system, are brighter than the type II supernovae, but some of them could also happen in the older parts of Galaxy which are hidden due to the buildup of the dust and gas.