Why black hole merges happen so frequently? We just started registering them and got three events already... Mass of Universe is estimated to be of 6e51kg. Ma

Why black hole merges happen so frequently? We just started registering them and got three events already... Mass of Universe is estimated to be of 6e51kg. Mass of Sun is 1e25kg. This event is about 50 Sun masses. So that one event is about morphing 1e-26 part of Universe. I suspect that matter collapsing into black holes happens significantly more frequently than that. Do we have enough non-black-hole matter available for our (humanity) life time? Yet worth to mention that black holes "return" mass by not only Hawking–Zel'dovich radiation but also by such events - this particular merge emitted 3 solar masses as energy.