An example of passive voice would be “Why programming is done by me.” And of course no one would write that.
You may prefer “Why I program”, which is indeed more concise and straightforward. But that's a stylistic preference, not a difference between active and passive voice.
For a similar example, consider “Why I do science”. Here there isn't a convenient way to shorten it, but it's still active voice.
In general, for any X, “Why I do X” is active voice, and “Why X is done by me” is passive voice.
He probably didn’t fail at grammar in Spanish, his native tongue. Writing “why I do programming” in an ESL evaluation may get a few points docked off but unlikely to be grounds for flunking.
An example of passive voice would be “Why programming is done by me.” And of course no one would write that.
You may prefer “Why I program”, which is indeed more concise and straightforward. But that's a stylistic preference, not a difference between active and passive voice.
For a similar example, consider “Why I do science”. Here there isn't a convenient way to shorten it, but it's still active voice.
In general, for any X, “Why I do X” is active voice, and “Why X is done by me” is passive voice.