While SMBH at the center are common, it is believed that there are plenty of galaxies that don't have such a black hole including spiral galaxies. For example,

While SMBH at the center are common, it is believed that there are plenty of galaxies that don't have such a black hole including spiral galaxies. For example, M33 [1]. The upper limit on its central black hole is ~1500x of Sol and it's widely believed right now to just not have one. By comparison, the Milky Way’s black hole is 4 million Sol masses and our galaxies SMBH is quite tiny by comparison to many galaxies. [1] https://www.science.org/cms/asset/7c8770b5-a357-40f5-a491-19c2c4a6e7de/pap.pdf https://www.science.org/cms/asset/7c8770b5-a357-40f5-a491-19...