People get this idea because they see companies create programs over and over. The same applies to buildings, building are created reliably over and over and over. If all that stands between you and success is a building, or some software, you're in a good place.
The difference is people have respect for the value of a building, they understand the cost, they understand the reason for those costs. People don't have the same understanding for software.
Nobody would say "I thought you could just throw a 4,000 square foot house together for me, it's nothing special, just a common house", but apparently some people will say "I thought you could just throw a website with a database together for me, it's nothing special".