I can see this is a console-peasant, let me handle this one
you see that unlike you that whom I assume is a console-peasant we the PC MASTER RACE does not want to use more equipment than our glorious PC, the point of the PC is to have all in the same place and dont bother with things like a tv or something else that is not a PC.
Now comes the mobile phone, as people tend to upload pictures of their glorious bodies or bother us with things like kik or sms we now have to have one hand on the mouse and the other on the phone, meaning we will now be fully occupied with our hands.
A keyboard and mouse configuration helps us watch pictures of kittens and write comments about how other people are wrong and between the writing we can pick cheetos up from our bellybutton-bowl but now to hold a phone in the hand that does the cheetos picking, and that is just not right.
And for your second question, simply to run apps.