Wouldn't you like your build to be set apart from everyone else? Don't you want to make the most efficient horsepower for your specific setup? Not all car builds are created equal, so why be slow like the guy next you using that same ole 'off the shelf' camshaft that wasn't designed for your actual setup? Camshafts are a very important piece to your build, and should always be custom spec'd based on your exact setup, and for what it is being used for.
Most off the shelf camshafts are designed to give the average user an average experience. The problem with that is that any little change to a setup and the optimal camshaft specifications change accordingly. Not all cars are average, some are purpose built drag racing cars, some are meant for roll racing, some are meant for circuit racing, some are built for drifting, some are simply built to just have fun and sound good in the daily. In each of those cases we would actually recommend a different camshaft profile. Due to this we highly recommend all of our clients to go with a custom spec/grind camshaft.
Sometimes your perfect camshaft will actually be an off the shelf camshaft, and if we can save you the money by going with that cheaper option we will let you know!