Because there is usually the head of some emperor or king or queen on the other side. To call the opposite side "tails" just seems to be as good as calling it anything else.
tails
The probability of the coin flip being heads or tails is 100%.
Heads have a person on it. Tails have something else on it.
For a normal coin, it is 0.5.
Since there is only 2 sides to a coin...tails will come up 50% of the time.
Heads. The obverse is the front of the coin. Its opposite (the back of the coin) is the reverse.
tails
The probability of the coin flip being heads or tails is 100%.
Heads+Heads ; Heads+Tails ; Tails+Tails
tails
The probability of two tails on two tosses of a coin is 0.52, or 0.25.
Heads have a person on it. Tails have something else on it.
For a normal coin, it is 0.5.
Assuming the coins are fair, two-sided coins, and landing on their sides is not an option, there are four possible outcomes if you consider coin a having a head and coin b having a tail being a different instance from coin a being a tail and coin be having a head. Here they are; Coin A | Coin B Heads | Tails Heads | Heads Tails....| Heads Tails....| Tails
Since there is only 2 sides to a coin...tails will come up 50% of the time.
The probability of a fair coin landing on heads or tails is even, i.e. 50/50.
Heads or Tails