... because happiness is a result.
It's a result of living a life that matters.
It's a result of doing work that matters.
If you are not living a meaningful life or doing meaningful work, you cannot find real happiness. You may have all the success in the world (the money, the promotion, the recognition), but still not find true happiness.
The happiest people who ever lived were those who lived their lives with purpose and did work that made sense to them and made a difference to other people's lives.
Pursue those instead.