I have never understood gambling on mobile phone, because it is such a small screen.
Optimization! Gambling sites optimize their sites in mobiles in such a manner that you won't really feel inconvenienced by the small size. It's way easier to start gambling on mobiles when compared to gambling on laptops or desktops.
but phones are really the wrong medium for it either way.
It does feel more serious when you are viewing a large screen and using many buttons to delegate your actions.
I sometimes wonder why people are starting to shift away from computers/laptops and adapt more to smaller, mobile devices.
I disagree. Mobiles are an awesome medium for gambling. You can literally gamble anywhere thanks to mobiles, but the same cannot be said about laptops or desktops. Portability is the primary reason which adds an extra layer of convenience.
Secondary reason is battery life. Mobiles usually last a longer when compared to laptops while on the go.