I suppose it depends on how one defines showing love to their parents. One person may consider taking their parents back and forth to the grocery store, doctor's visits, and helping them with their finances as showing their love.
Another person may put their parent in the best nursing home they can afford. Not everyone is financially in a position or capable of turning a room in their home into a hospital room. Different people have different expectations.
The truth of the matter is peopple have children because (they) want them! For anyone to turn around and make it appear as though they did the child a "favor" by bringing them into world is being disingenuous! I've heard my own peers say they thought I should have kids so I would have somone to "take care of me" in my old age. Ironically most of the people in nursing homes had children!
Personally speaking I chose not to have children but if I had I would not expect them to sacrafice the prime of the life feeding me, bathing me, wiping my behind, and dressing me. I would have kids because (I) wanted to be a father and not because I expect some return on my "investment". Love is giving freely. We accept the love that people (give) us. Some children will bend over backwards for their elderly parents and some will not visit them much at all. A lot of how an adult child behaves with their parents is often a reflection of how the parents treated them during their childhood and young adult years.
The days are gone when an adult child who resented their childhoold will care for a parent out of a sense of (duty or obligation). Odds are they will distance themselves from those who made them unhappy.