I think the idea is just to make things easier, so .tel becomes a kind of yellow pages for online businesses.
As a way for users to immediatly reconise a sites content from its tld.
So whens someone sees xdnet.tel they know its contact detauls when they see xdnet.co.uk they know its a UK company.
If i had xdnet.mobi it would imply xdnet was a mobile/telecommunications company.
.tv media (Even tho its a country code i know)
etc.
Which is also why there is the proposal for .xxx so adult content can be seperated.
Its all to make this more organised and easy to find
Dan