Because of copyright issues. You can see that his early-stage MH was all derived from L-GAIM, which copyrights are the property of Sunrise. (Bash, Cross Mirage, LED Mirage, AUGE, JUNCHOON, A-Toll...etc.) Hell, he even committed that Colus (XX)VI "is" the counterpart of the L-GAIM's main protagonist Dabba.
Base +7, kondoriyano +6, Xaive +6, Rivivalistic -6