Because you can do anything on your smartphone like your laptop.
These are advantages of smartphone over laptop
1. You can call via cellular network, not on laptop.
2. You can have longer battery life on smartphones than laptop as laptop drain more battery and fast.
3. You can have almost every type of app in Play Store to do your work.
4. Easy to navigate between work.
You can pretty much do everything on smartphones same as you do on laptop.
I have my laptop and PC.
But, I most of the time use smartphone instead of laptop or pc as it takes formality to handle laptop or pc.
But, with smartphone you can do your work while lying on your bed and fast and easily.
But, it's your choice, after all.
Cause if you want to do gaming laptop is much more convenient as most pc games cannot run on smartphones.
But, games can run smoothly on smartphones rather than on laptop as laptop requirements are higher for different different games.
So, it totally depends on you what you want to do with laptop or smartphone.
The choice is yours but I PREFER SMARTPHONE.