Why are underdog teams having such a hard time winning?

[WinJonny]

How is it that underdogs have such a difficult time winning?

In minor league baseball, betting on underdogs
If you are betting on underdogs, don't limit your attention to the top leagues like the English Premier League, Bundesliga, or WTA. The best odds are typically found in lesser leagues because favorites frequently outperform underdogs by a wide margin. Due to the near impossibility of underdogs winning the game, they are given extremely long odds.

 

[Hardexy1]

Underdogs team always have more difficult time wining because it's always not easy for them to win their bet, they struggle more to win every of their game because they have lower tendency of winning