If this were a party, Canon mirrorless cameras would definitely be "fashionably late".
Virtually every other camera company (Nikon included) had released a mirrorless camera before the arrival in late 2012 of the Canon EOS M.
But why? Why would the top manufacturer of compact digital cameras and digital SLRs be so behind when an opportunity to dominate yet another part of the digital camera market presented itself?
You'd have to ask Canon management to be sure, but - based on comments made to the press - it appeared that Canon wanted to focus on making a smaller digital SLR rather than diving in to the mirrorless market.
This makes sense - due to their smaller size, mirrorless cameras require a new type of lens. While regular digital SLR lenses CAN be used, they require bulky adapters that diminish the camera's portability.
By creating a Canon mirrorless camera, the company has had to start over (in some respects) with their lenses. If you get a Canon DSLR, there are hundreds of lenses to choose from. With the EOS M, there are two.
Yes, you can expect this number to grow over time, but only if Canon discovers that the mirrorless segment is worth their while.