Of course not. There’s nothing stopping you from picking up the phone and calling your parent right now and telling them of your appreciation for them. Or expressing a deeply felt emotion when with them (such as telling them how much you appreciate spending time with them).
I do this with my mother all the time (and vice versa), and we have a wonderful relationship.
I certainly do not subscribe to these silly marketing holidays and the associated bullshit. My love is better expressed via words or effort than by spending $5–10 on a mass manufactured card made by someone who only wants my money. If I feel creative I will make the recipient a card or present with materials I have in my giant art stash. This to me is a much better present, not only is it one of a kind and custom made to the person, but I feel that the expression is more sincere when you actually put effort towards something versus going down to the store and buying a funny card with a cat on it.