Change in management.
At management levels, it seems that every passing dog has to lift their leg on the tree trunk. And that generally means doing things differently. Nothing ever has a chance to become practice as careerists move from position to position. So even when an identified "best practice" (though, color me cynical about their identification) comes in under a new leader, it will be replaced just as soon as the next one comes in.
We have surveyed federal employees every 3 years since 1999, and one of the consistent observations is that the more supervisors or managers employees report having during the preceding 3 years, the worse a wide array of other workplace indicators are, including perceptions of employee-supervisor communication, autonomy, innovativeness, support for career development, and knowledge-sharing. Similarly, when asked about the impact of "instability within the organization" and "constantly changing priorities", those who report these bigging a bigger impediment to their own work performance also report a host of other things in their workplace being worse.
You can throw all the best practices you want at an organization, but the likelihood of them sticking is a function of the stability in leadership.