To dispell the American perception of Soccer:

They're not flopping all the time. It's a contact sport and sometimes they get the wind knocked out of them or really fucked up. In this past MLS final the keeper of LAFC got a broken leg (and a red card for illegal contact) trying to stop Philly's striker by sliding into him. Look at pictures from the Brazil/Serbia game of Neymar's ankle. It's swollen to the size of a grapefruit. In the past week of just a handful of World Cup games I've watched, I've seen dudes get kicked in the face, head, and dick. People ramming into each other at full speed. And getting cleated anywhere fucking sucks. There's a player for Wolverhampton that's still wearing a brace for a fractured skull and that motherfucker is still playing. Some games are physical slogs, it can actually get real nasty.

Now. As to why they'll flop and/or feign injury:

1. fishing for fouls. And sometimes you kind of need to do it because you were fouled but referees are pants on head stupid.

2. Time wasting. I like to say a team is 20 seconds away from scoring at any point in the match. You're up by 1 goal and it's the final 5 minutes? Got some rough contact? Better go to ground to burn the clock (and take a little break). It's not even the main method of time waisting. If you're up a goal, and you get a set piece (corner, goal kick, free kick, throw in, etc.) You taaake youuur tiiiime.

I'll say this: if you actually watch a game, they really don't flop as much as my fellow Americans like to think they do. They spend most of the time, you know... Playing the game. And it's exciting to watch because there's always something happening instead of people standing around or commercials every 30 seconds like with NFL and baseball.

There are rules for egregious flops. Simulation (faking illegal contact) gets ya carded. And the practice of flopping ain't going away. It's part of the tactics of the game, really. Not that they practice it in training or anything. And like I said, it's not like every bit of contact results in a player dropping to the ground and playing hurt. They go at each other hard most of the time. The only protection they have are shin guards. The rest of the body is exposed to abuse. You get tripped up while you're sprinting, it's going to hurt. Dude steps on you literally anywhere, it's going to hurt. NFL players have the luxury of play stopping for a minute between plays to walk it off when their bell gets rung. Soccer players don't. Hell, the game even keeps going if there's a man down. They won't stop play unless he doesn't get up for a while. Or if it was contact to the head.