why was the last song and the Justin Bieber movie shorter on dvd then in theaters?

why was the last song and the Justin Bieber movie shorter on dvd then
in theaters?

I can defianatly tell the difference in the last song because i
remembered scenes that they didnt have on the dvd.

and the JB movie definatly had a lot more in it and i am kinda
dissappointed.

There are no deleted scenes or anything...