Many people, such as myself, prefer to see a REAL image through the viewfinder, rather than a replicated one on a tiny electronic screen with limited resolution. It will be quite some time before there is a major shift from DSLR type cameras to mirrorless cameras, and the two service partially different demographics that simply overlap...neither cover exactly the same range of photographer types.
This is the point for me too. I simply wouldn't use one 'cos I often stand in a corner and wait for the perfect expression when doing a wedding. I need to see massive detail to be able to do that. Plus, I want to use my camera as it is, ergonomically.
Fundamentally I'm not going to take a camera system which is worse than what I have right now.
I've no doubt that mirrorless cameras have their market - and good on those manufacturers who spotted the gap - but it's not something that most pros are going to want to use for the majority of their work. I might have one as a second camera for hols and stuff, but it's not going to be my tool of choice.