I would say otherwise - nobody actually should. I dislike the word "should" here, yep it's the first factor I may dislike - if somebody says what I should do and what I should not. I believe many others are on that factor, too. I should only do what God says me, and the same I want from the others. Like any software, miniBB is a factor of choice, of taste, priorities and web experience. You can build a good forum, bringing good profits, with the other software, too; but definitely, it will be different from miniBB, which is just like a tool, an instrument, and like with any other effective instrument, you need some knowledge and tension to use it.
But I think, in comparison to the competitors, you definitely may like miniBBs comfortable interface and the basic layout. I personally like how it works and looks and how quickly it allows to moderate multiple forums at once. So far it also perfectly works on i-devices, and it's coming with the ultra-simplified interface for older mobiles, and all that phones having simple browsers.
Well, in common I love the idea that the forum software continues its life on mobile devices, it proves the fact that this type of program still stay one of the best for keeping and sharing information, and in 2001 it was a correct choice to start to work on such type of the software.