Because there exist so many schools of programming and so many deep philosophical considerations what makes software good vs not good.

Basically, software created by programmers who are more on the artisan side often deeply encodes what they value in life and what they don't.

So, finding a "good" programmer for a company means finding someone who is skilled in programming, and who has very compatible deep opinions about life and everything.

Also, many exceptional programmers are not good, obedient workers in a "software factory"; this is another consideration that you have to keep in mind.