Why not to use Small MOBILE batteries in Laptop for more power and smaller size

It came to my mind many times that why we are still using those mammoth batteries in laptops whereas in mobiles they are so small. Consider my laptop, I have 6000 mAH battery in my laptop, used to give around 4-5 hours backup when was new. On the other hand, I have a mobile which has 4000 mAH battery and yet very small.

The size of my laptop battery is so big if I compare to my mobile battery that you can get whole mobile fit in to battery of laptop alone. Then why still manufacturers are using such big batteries in laptop when they can have much smaller battery in mobiles.

Why not to use two 4000 mAH battery laptop instead of one big 6K mAH , that will give you 8k mAH and yet laptop will be lighter.

Just ranting out, now I will search google for more information, meanwhile please share you views here.

I don't think it is as simple it may look. mah is not the fit for all measure to calculate battery's capacity. It depends upon how much current battery is supposed to provide also. So it may look same but is not same at all. That is the reason that laptop batteries are bigger. But newer laptops have smaller batteries yet not that smaller as mobile.

If you really want to know what is power of battery in real then look for Wh, it is called watt hour capacity which calculate the real capacity of a battery. So, eg, if a phone uses 1 amp then 2000mah battery will last 10 hours, however, if that very phone uses 5 amp, it will drastically reduce time and it will last only 2 hours instead of 10.

I hope this makes sense.