He doesn't hide his work but doesn't share it with anyone.

At the office, he always talks about his side income, proudly sharing how much he earns and so on. But he’s never once asked me if I want to do the same. Frankly, our relationship isn’t bad, so I don’t understand why he’s keeping it a secret. Isn’t it strange to talk so much and not share? Do you think I should say something, or is everyone entitled to choose what they want to do?