Why jQuery Mobile Why not jQuery UI ?

Why jQuery Mobile Why not jQuery UI ?

I hope this question does not rub folk up the wrong way however I have been developing an application that has both desktop and tablet audience - until now I have developed using jQuery and jQueryUI. The tablet dependancy has until now utilised Dialog and Buttons and for the most part, delivered what I want.

My concern is as my dependancy increases (meaning I use features beyond Dialog and Buttons) that I will find myself applying band-aids to my tablet target code which might not otherwise be required if I had developed using jQuery Mobile.

Is there something I am missing? Does jQuery Mobile 'compete' for part of the jQuery UI's audience or are there real added advantages of one over the other?

Comments?

(thanks)