Because dark matter is too convenient, and it's not like LCDM prediction are 100% on the money. http://backreaction.blogspot.com/2017/01/the-bullet-cluster-as-

Because dark matter is too convenient, and it's not like LCDM prediction are 100% on the money. http://backreaction.blogspot.com/2017/01/the-bullet-cluster-as-evidence-against.html?m=1 http://backreaction.blogspot.com/2017/01/the-bullet-cluster-... Another big problem is that all LCDM predictions (MACHO/WIMP) were disproven but it still remains a theory. Now we need energy too high to use in universe. It's eerily similar to Phlogiston theory that at one point was considered to have negative mass.