Because for at least the past 2 season its basically been the same 25 champs banned/picked every game. If they aren't banned, they are picked. 16 champs are banned/picked every game, that leaves 9 champs that are interchangeable in the usual lineup.
But wait the nay sayers shout, there are a ton more champs picked than 25.
Ok your right. Over the course of the summer split, I beleive 67 champs were picked/banned out of the 120+ that are in the game. However, the pick/ban rate for those champs varied immensely. Champs like Lee Sin, Zed, Elise, etc had enormous pick/ban rates, being in almost every game. By contrast, other champs that were selected such as veigar were picked maybe a handful of times, never banned and almost exclusively picked by one pro because its a niche pick. So, in reality, it really was just about 25 champs every game that were seeing action.
I love watching pro games, but watching games were every game looks so similar to every other one being played across the entire season gets to be a bit boring. So, I humbly submit this change to the LCS series games.
Each time that a champ is picked/banned, they are disabled for all following games in that series. So, each game, the champion pool decreases by 16 champs and no game will feature one pro playing the same champ over and over and over. In a best of 3 series, at least 32 champs will be picked or banned, at most 48. Way more diversity. In a best of 5, 48 champs will see the rift (or be banned). Or, if it goes to 5 games, a whopping 80 champs will see some form of the action.
"but this will stretch pro's champion pools to limits where they can't even play"
Not really. Sure, they won't be on their mains or whatever is FoTM, but I've seen pro streams. They can play way more champs than what they actually do in the LCS, they just don't play them in the LCS because they are more comfortable on their pool of 4-5 main champs.
I might get downvoted to oblivion by people who like watching LCS the way it currently is, but having watched it for years I can honestly say that it has gotten stale and watching games now looks basically the same as it did 2 years ago, barring a few changes to the main champion pool. Change is scary, but variety is the spice of life, and LCS desperately needs variety.