I'm of the opinion that if you are not trying your best, even in practice, you're not trying hard enough. Considering some of the responses I've seen when I say that, I know I'm not part of the majority.
I played a game yesterday as Lux. The team wasn't on-the-ball coordinated. But they were winning more of the team fights than they were losing. But they did lose a few here and there. The three main aggressors on the team would attack players and things like the dragon and other jungle targets, but they would not push the base. At the thirty minute mark, my team started getting Aces. But they still would not push the base.
At the thirty nine minute mark, I said "Can we push now?" The enemy team had managed to take out all non base turrets and large minion groups were becoming a problem. "Ok," they said and took out the middle inhibitor turret. But they wouldn't push further than that. In fact, they wouldn't even enter the base. If they killed three or more enemies, they'd dash in to the jungle, then hearth back to the base. I kept telling them to push the enemy base. Fifty minutes in, we'd lost all but one base turret and sneak attacks were hitting our inhibitors. As Lux, I couldn't solo a charge. "Please attack! They're whittling us down to nothing." Even after an enemy disconnected and left it a 4 vs 5 game, the team still would NOT push the base.
Now maxed out, we started losing to the enemy team. Sixty five minutes in, the enemy team hit an Ace (they finally got me once,) and destroyed the Nexus. I was mad. Very mad. The others fooled around long enough and it finally cost them. One of them said "it's normal, who cares?" Post game, I told the other team that I had been telling my team since the half hour mark to storm the base. "We know," said one player. "We kept waiting for it but it never happened." I honored the other team. Me, I got nothing.
So, all that goofing around cost us a win. That was a very disappointing game. Some of us DO care about trying our best regardless of what type of game it is. If you practice like you don't care, what do you think you'll do when it's time to be serious? You've only practiced goofing off.
(who I loathe) and my friend full AP 
, we both rolled 
lol.
bitching about our comp in the team builder lobby forward. As karma would have it, try hard 
, failed, and was 3 levels behind the support the entire game and completely useless. Our mid 
, top 
also lost their respective lanes but they never complained, they were very chill.
, carried the team to a victory, and had more fun playing this match then I had in any of the 100+ ranked matches I played all S5.