Many serial number protected commercial applications have had their algorithms for validating a SN cracked and Key Generators spit out any number of valid serials for them.

Why would they use an fixed algorithm like that instead of using a good random generator and maintaining a database of valid codes? Perhaps they want the redemption side to not be reliant upon a backend code lookup and validation system (due to uptime, performance, etc...). Perhaps they thought no one would break it, and that would save them from having to build a high availability, low latency, high throughput, lookup system with some amazingly large database tables.