Turrets are the biggest factor when snowballing

As what is very known by a lot of players, turrets grant 100 global gold and 225 local gold, while a kill is 300 gold.

While this seems somewhat the same, the turret grants 500 total gold to your team, giving your team a pretty noticeable advantage over the enemy team, not only in gold, but also map-wise. You're allowed to move further into the enemy jungle when towers are down. Also with the addition of first blood tower, gold-snowballing by towers has increased. It isn't uncommon to see a team stomp another team with 2 more towers, but 10 more deaths.

It's problematic because it removes champions that wants to play alones purpose (assassins and duelists). They can apply pressure when diving the enemies or catching them out, but they lack the teamplay part of the game. The teamplay that shines through the compeditive scene, which is why split pushing comps are a part of the past.

We all know the best way to take towers is to group up, kill the enemies and hit the tower. Early game, grouping is still a big part of the game. You often see how most games are won by the mid roaming bot with their jungler to 4 man dive the enemy and get their tower first blood and then get drake ass the head on the nail. In LCS, even the top laners follow up by using their teleports to help their bot lane.

The best champions and comps to dive and teamfight for objectives are a tanky frontline and a ranged backline. No duelists or assassins. Which is why taking over the game with these types of champions is so unneccesarily important while you might as well could have picked a ranged damage dealer with a much better time in the teamfights.

Getting towers puts so much pressure on the enemies alone, but when you count the gold a tower gives + first blood tower gold, that amount basically carries the game into a onesided stomp where you get one tower and basically already win the game from there.