Elena - I have seriously been wondering that.
None the clumps (most of mine are NOT clumps but 2-5 fans) are big enough that they need dividing. Most of mine are evergreens or semi-evergreens. Ironically, most of the few dormants I have bloom every year! Go figure on that one.
Here is a list of those that have yet to bloom for me after at least 2 or more years. (I noted any that may have bloomed once but haven't since.):
Fol de Rol (This one bloomed the first year I got it (2014) and hasn't bloomed since.)
Judge Roy Bean
Lillian's Thin Ice
Paper Butterfly (barely bloomed last year and didn't at all this year)
Purple Rain Dance
Sings the Blues
Most of them are small or medium clumps of at least 5 fans. I guess the list isn't as long as I thought. Looking at my garden though, even many of the newer ones didn't bloom for me this year.