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There is another side to this question that is on my mind, a lot, lately. At many of the companies I'm familiar with, either first hand or anecdotally, key decisions are made before the PM is involved, and once the project is over the project manager and most of the project team don't hear anything more about it unless something breaks. The PM can help put the BRM plan in place, but may never see it again beyond 2-4 weeks after project conclusion. The side I'm thinking of is motivation.
Working in IT, for a lot of what we deliver, we just assume it's useful, churning out code day after day. There can be a big disconnect between what we do and seeing how it adds value to the company. Is it helping achieve strategic objectives or is it just a useless feature that got approved due to a HiPPO decision? This doesn't happen just in IT; the disconnect between work and value can be highly demotivational in any department. Depending on how things work at our companies, we might have some influence on this. Some of us might even have some control over it. But, largely, these are organizational decisions that many project managers don't get the opportunity to participate in. But, if you can help team members create that mental connection between their day-to-day work (project or otherwise) and the success of the company, you will find that it is one of the factors that can motivate your team members.
What I'm doing at my current employer, that I wasn't able to accomplish at prior employers (due to factors like how the role of PM was viewed and company politics), is working with the leadership team to make the connection between company strategy and the project work we do, and make it visible to the teams. Call it portfolio management lite. We have a backlog, if you will, of objectives in various stages of readiness. Our teams know when we're working on one of these issues and what we're hoping to accomplish. We're setting up dashboards to track impact of the changes. We don't always have clear ROI defined, but we're working on it.
Obviously, this does not motivate everyone, but it does motivate me. I've been at companies where my suggestions to move in this direction were ignored. At one company, after reviewing the "strategic" plans (highly siloed, if you ask me), and sharing feedback and recommendations with my director, my director got in trouble for sharing the plans with me, like they were some kind of secret.
To tie this all back together, for those that aren't aware, the tools and processes to help "make sure your project delivers its expected benefits when your project ends" exist and are fairly easy to find. The biggest obstacle to being able to do something with these tools and processes is organizational change. Maybe you'll be able to bring it up and people will say "Great idea! We hadn't considered that before," and you're on your way. But, at some companies, this will be a major transformation and something project managers will not be able to initiate on their own. In these cases, having a good grasp of organizational change, or someone who does, and someone to help champion the cause will be key to getting traction.