Thomas,
I have worked with lots of private clubs and almost without exception a membership vote is required for any kind of significant capital spend. Actually most of my time is spent educating and helping cross sectional committees gain knowledge and to obtain membership support for course improvement projects.
Public access courses that have a single owner are a different matter. In those cases I am working with the owner and he or she is making the call. Even in these cases the Superintendent is always involved as well as sometimes the head pro. Golf is a tough business these days and you have to be smart with spending. The days of architects developing beautiful extravagant master plans are very limited. There are many times where I would love to get really creative and make dramatic recommendations for improvement. But if all that plan is going to do is hang on a wall or put a club in financial jeapordy I wouldn't do it. I am sure many others here operate the same way. As Tom said, sometimes we are talking people out of unnecessary change and expense like adding crazy back tees for the six golfers at the club who will use them or rebuilding greens when other less costly and more prudent options exist.
There are always exceptions like Merion spending $15MM but 99% of the courses out there don't and can't operate that way.