The career should be a secure future where the career should be built around that. One's personal decision is the most important one behind building a career. Many people spend time gambling but they do not prioritize gambling behind career building.
It is possible to build a career in gambling when there are profits from gambling but no losses. But in every gamble there will be both profit and loss but to build a career there must be a guarantee of huge amount of income on gambling. It is not possible to guarantee a huge amount of income on gambling so no one would want to build a career on gambling.