Ban on dialect TV prog to stay

Whilst now daily u can hear the “Wa men ti Wa men ti” 我问天 theme song for the popular Taiwanese TV drama <爱> yet on local variety shows when they invite the actual Taiwanese singer of the show to perform, he is asked to sing the mandarin version?!? (-!-|||)

Also some foreign films /Korean tv drama is shown in dual sound channels. So why can't those shows in dialect be offered in a similar fashion?

Nowadays many younger generation can't speak their dialect. All things being equal, say 2 businessman goes to China to negotiate a contract with same terms. One can speak the China's counterpart's dialect whilst the other can't. Who do you think will be most likely to succeed?