Why is it so hard to get your team to group and push objectives?

I honestly don't understand the mindset of people that absolutely refuse to group up as a team, push objectives and fight all together and press advantages. I understand there are appropriate times to rotate lanes, split-push and such. However when you're consistently getting picked off because everyone is off roaming alone chasing kills, how do people not learn from their mistakes?

Now obviously I am no big shot or high ELO level League player nor do I pretend to be, but all of this to me seems like common sense. My friends and I all share stories of similar situations where we lose easily winnable games, where you've got quite the lead and an advantage to press, but instead everyone seems confused on where to be and what to be doing in the late-game.

Some people naturally are not going to listen no matter what you do or say, despite how you go about it, but does anyone have /ANY/ advice on how to go about at least attempting to bring the team together? I've tried to grit my teeth and act as nice as possible and be direct when shot-calling. Not spamming, nothing like that, but I'm tired of losing games that should be in the bag, but you can't close it out because your team is all scattered either chasing kills or just farming needlessly. etc. etc.

Anything you can give to help me either make better shot-calling decisions or make the team more attentive and listen better when it comes to grouping and teamwork, please help.

Even when I'm carrying the match for my team, that doesn't seem to make a difference whether they listen or not. It seems to be extremely rare that I find a team that just cliques, ya know?