In the early days there were all sorts of anecdotal stories about the unreliability of flash. History has shown that some of that was undeniably true. Manufactures haven't helped themselves by being, shall we say, somewhat obscure with their specification and application data. I certainly get the impression that at least some of the manufacturers either didn't fully appreciate or care about data write / rewrite implications of some applications.
The result was that there was - and still is - deep suspicion over these devices.
Spinning rust on the other hand is well known, trusted, and more important, the various failure modes well known.
IT is a somewhat conservative profession, particularly where data security is concerned. (I wonder why?)
Early devices were also well overpriced and of very low capacity compared with spinning rust. That is changing very quickly.
There is going to be a tipping point, and I think it's quite near - unless flash hits a major reliability problem as capacity increases. I'm assuming that capacity will continue to rise and relative prices fall.
Or if some of the "real soon now" technologies really do come on stream.
Personally I think that the tip will be from the other side. I'm getting increasingly concerned about disk reliability as capacity increases. I've just got a gut feeling that we are quickly reaching a limit with the physics and chemistry of what is after all a mechanical device.
We live in interesting times.