Why doesn't my boyfriend give me his active whatsapp account phone number?

So my boyfriend has a second mobile, which I don’t have its number, since he has not given it to me neither have I asked him to give it to me and with that mobile he has his active what sapp account and with the other mobile number that I have its not active, cause its an older small little phone (he did an account with the mobile number that I have but he never happens to use it as far as I can see) so the issue is that when I ask him when are you going to give me your other whatsapp (the active one) he beats around the bush and basically just says that why would I want it if I never call him enough or text him ( its kinda true I don’t call him a lot neither text him) But he doesn’t either, anyways
why would he not give it, to me its a normal thing between a girlfriend
and a boyfriend I suppose,he is 9 years older than me and I am 27 , Can this mean that he is possibly is hiding something from me?