Absolutely.
I've seen so many projects hindered by bad decisions around performance. Big things like shoehorning yourself into an architecture, language, or particular tool, but even small things like assuming the naive approach is unacceptably slow. If you never actually measure anything though, your assumptions are just assumptions.
Based on some places I used to work, upper management seemed convinced that the "idea" stage was the hardest and most important part of any project, and that the easy part is planning, gathering requirements, building, testing, changing, and maintaining custom business applications for needlessly complex and ever changing requirements.