That, and the fact that within any sector, fads tend to spread because organisations faced with a project often don't just work it out from first principles, they look at what other people have done in the same situation.
Also they're more acutely aware of the downsides of whatever system they are currently running than of the problems of an unfamiliar system. Greener grass on the other side of the fence.
And of course, there's always what CS Lewis dubbed "chronological snobbery" - the idea that anything new and fashionable must by definition be more advanced, efficient and progressive.
It's like the architectural fad for flat roofs. People relearned, the hard way, exactly why they weren't ideal in a wet climate.