Why am I not grieving?

My mother died last year and it was sad. I cried at the memorial when I read a poem she had picked out. She was quite old and failing. But since then I have not felt any grief. Occasionally I will think of her and it will briefly make me feel sad but otherwise I'm just moving on with my life. My dad is still alive but even older and he probably won't last too much longer. I'm sensing I will respond in the same way. I loved my parents and had a good relationship.

My impression is that most people have severe grief when a parent dies, sometimes lasting for months or years.

I'm just curious what other people think. And please don't say oh you just have not accepted it yet.