html - Why do I have to separate the -input-placeholder css tag for each browser? -

i tried setting input placeholder color using following css

input::-webkit-input-placeholder,      input:-moz-placeholder,      input::-moz-placeholder,      input::-ms-placeholder {         color: black;      }

<input placeholder="some text">

but not work expected in chrome 59. instead, have write

input::-webkit-input-placeholder {      color: red;  }  input:-moz-placeholder {      color: red;  }  input::-moz-placeholder {      color: red;  }  input::-ms-placeholder {      color: red;  }

<input placeholder="some text">

why have write code this?