Strategic methods and tools are sufficiently well known and can easily be obtained
Nothing new for decades
Strategic techniques and methods are well known and are freely accessible to everyone, but these only provide the place setting, rather than the recipe for a gala dinner.
Many theories sold as new approach are old wine in new skins. Apart from some reworked methods and tools, there have been no significant innovations for years.
The tools are easy to learn
It is not the concepts and tools per se that are the crucial factor for the effectiveness of a strategy, but how and by whom they are applied. This is something that has to be learned sooner or later by the employees since the external specialists are long gone by the time that the concepts and tools are being implemented and applied.
Most larger companies today have departments dedicated to business development which can provide access to all the necessary tools. The skills required to coach and steer the process are usually available internally.
External specialists can be called on if required, but their main role is to coach and act as a sparring partner.