Soccer tournaments usually all follow the same platform. The initial round is referred to in the group stages, where a group of 2-4 teams each play one another. A win is worth 3 points, a tie is worth 1. The top two teams in each group typically advance to the knock out rounds.
But since the games are already 90 minutes of nearly constant action, a single instance of overtime would pretty much cripple a teams chances of advancing through to the next rounds. While the knockout rounds require a winner, the group stages do not and so a tie is vital.
Consider the USA men's team schedule for the World Cup:
June 16th vs. Ghana
June 22nd vs. Portugal
June 26th vs. Germany
July 01st vs. Belgium
On June 22nd, the US tied Portugal 2-2. Had they played the 90 minutes of regulation time, then the mandatory 2-15 minute halves of overtime, and possibly go into a penalty shootout from there to determine a winner, there would have been no chance they could have even competed against Germany.
Keep in mind, they lost to the Germans 1-0, 4 days after tying Portugal, and the Germans later went on to destroy Brazil 7-1.
If you think this makes no sense, consider this. Go outside this weekend in the intense heat and run around the block for 90 minutes, taking only a 20 minute break. Then run around again for 30 minutes, with only a 5 minute break between.
Then four days later see how you feel.
In professional soccer everywhere in the world (with the exception of Major League Soccer in the US because there are not enough teams), if you do not perform well in your league, you get 'relegated' to a lower league. The top 3 teams from the league below you come up, and the bottom 3 teams from the premier league go down.
This past year Fulham, Norwich City, and Cardiff City were relegated from the English Premier league and Leicester City, Burnley, and Queens Park Rangers were promoted.
In American English speak, consider this loosely accurate metaphor. Imagine if the 3 teams in the MLB that had the worst record in any given year, were relegated to play in the AAA baseball league, and the 3 top AAA teams were promoted to play in the MLB for the upcoming year. (It's not 100% because AAA baseball teams are really feeder clubs for MLB teams, but it helps to illustrate the concept).
This is a big deal because obviously playing on the biggest stage is where the fans are, and where the fans are, is where the money is. Lucrative TV deals, sponsorship's, etc. What this system ensures is, that everyone who participates, is highly motivated to get MAXIMUM points from every game.
I live in Cincinnati Ohio, home of the Cincinnati Reds, and the Cincinnati Bengals. I used to be a football fan, but I could no longer stomach Mike Brown (the owner of the Bengals) pocketing massive sums of money, holding the fans of Cincinnati hostage for a new stadium while his team were perennial losers. Imagine if the Bengals were relegated to play in a lower league, without the benefit of TV deals and the ransom of blackout restrictions for televised games. Perennial losers like these in MLB, Basketball, and Football would be motivated to get everything out of a game they could. But because of the disparity of wealth in the leagues, you can't beat the big boys.
This is why a tie is vital. Consider a team such as Burnley. They might be thought of as your Milwaukee Brewers, a smaller team with a smaller fan-base and smaller income. In contrast Manchester United is the Soccer equivalent of the Yankees. The Brewers start the season with little chance of coming in ahead of teams like the Braves or Yankees. But could they over perform and fight to a draw, it would be a real victory for the Brewers, and they would walk away with something from the game. With 3 points for a win, 1 point for a tie, in a way it makes every game all that more important for those smaller teams. For the bigger teams, it makes a draw even worse, because getting 1 point from a game that you should have got 3 from could cost you the title.
Just ask Liverpool this past year.
Exciting seasons at both ends of the table:
This also means that both ends of the table are interesting in soccer, because you don't just care who's winning, you also care who's losing and about to get relegated out of the league. If you are a Bengals fan for example, and your team were battling against relegation, you would be interested to see how those final games of the season play out. If you can fight to get a draw against the big team battling for the playoffs, and that would keep you up in the league, you're much more excited about that game.
However in most American leagues, by about the midway point of the season, half the games being played have no value. If the Brewers and the Reds are out of contention for the playoffs, no one really cares about the result of that game.
But if they were fighting one another to stay in the league, you bet their fans would still care about who wins. As a result, this creates excitement at both ends of the table.