This is a good question, you might get different answers depending on who you ask. If you want to get really good at drawing you should draw anything and everything, however that doesn’t work for some.
One lady in my art class last year was very frustrated with herself as she was trying to draw animals. I asked her what she really wanted to draw and she said she didn’t know. After asking her what her hobbies were and what she did at weekends it turned out she liked boats and water. I suggested she draw boats and water and suddenly a light bulb switched on.