A Schematic design has been made, either from experience coupled with testing out application note blocks together. It could also be trying out an idea from a Magazine. If you have simulation tools, you may want to simulate parts of the design and iron out some flaws.
Now if this design is small or made of tested blocks and maybe verified by a seasoned designer. Then you can move to pilot production of 7 Nos.
If you cannot afford the risk and the cost of iterations. Sometimes making the PCB may delay the design so much, that the "Time to Market" will be too long. Then you lose out to the competition.
So... or Hence or even Thus ... A quick Breadboard or Stripboard testing not only validates your schematic, but improves your design skills by making you more familiar with the components and their behavior. The real world limitations and the non-ideal electrical specifications of passives, semiconductors and chips too. This brings us back to the word Didactic. We should always have both the feet on the Ground.
I wrote this note above inspired by the LochMaster, few years ago.
ABACOM LochMaster - BreadBoard projects
LochMaster 4.0 is a developers tool for BreadBoard projects. It has useful functions for designing, documenting and testing project