If there were plenty of these, gamma and x-ray astronomers would long since have detected the annihilation 'lines' at 511 kev and 1 Gev of electron-anti- electron, and proton-anti-proton annihilation. This is not seen, so that means that at some time after the Big Bang, any matter and anti-matter managed to segregate itself ( No known way to do this UNLESS matter and anti-matter are affected by gravity in different ways), or that starting from time zero, there has always been an asymmetry in the mater/anti-matter abundance. We know that K mesons decay into more matter than anti-matter end particles, so nature doesn't really treat matter and anti-matter the same way even though these forms are produced in equal numbers during 'pair creation' events. In a previous question I also discussed this.
As to WHY this is so, so that we only see matter galaxies, we have to say that this is simply the way Nature is. Just as the speed of light is fixed at the particular value it has. No explanations seem possible or likely in the future.