For convenience. It provides a 100% reliable stream, in full HD quality and with English commentary.
You can always find a stream but it's not always perfect and sometimes requires a bit of faffing about to get the best quality one.
Games like tonight, which are on their TV channel in the US, aren't available to stream online without TV provider details, which obviously you won't have.
You will be able to stream most (not all) Brighton games.
For the other games your options are Sky Sports, BT Sports or r/soccerstreams on...