当放大屏幕尺寸的时候，字体为啥不会随之放大？

相关代码：

* {
    box-sizing: border-box;
    padding: 0;
    margin: 0;
}

body {
    font-size: 12px;
    color: #5d655b;
}

 a {
    font-size: 12px;
    color: #686868;
    text-decoration: none;
    -webkit-tap-highlight-color: transparent;
}

[data-dpr="2"] body,
[data-dpr="2"] a,
[data-dpr="2"] input {
    font-size: 24px;
}
[data-dpr="3"] body,
[data-dpr="3"] a,
[data-dpr="3"] input {
    font-size: 36px;
}

li {
    list-style: none;
}

img {
    vertical-align: top;
    border: none;
    width: 100%;
}

html,body{
    height: 100%;
    width: 100%;
}

.header_container{
    position: fixed;
    left: 0;
    top: 0;
    width: 100%;
    height: 2.5rem;
    background-color: rgb(206, 206, 206);
}
.navbar{
    display: flex;
    height: 100%;
    justify-content: space-between;
    padding-left: .75rem;
    padding-right: .75rem;
}
.left_navbar,
.right_navbar{
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100%;
}
.left_navbar{
    width: 6.25rem;
}
.right_navbar{
    width: 4.25rem;
}
.download{
    width: 100%;
    height: 1.75rem;
    background-color: rgb(233, 201, 201);
    border-radius: 1.25rem;
    display: flex;
    justify-content: center;
    align-items: center;
}

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="css/base.css">
    <link rel="stylesheet" href="css/index.css">

</head>

<body>
    <header class="header_container">
        <div class="navbar">
            <div class="left_navbar">
                <img src="img/logo.png" alt="logo">
            </div>
            <div class="right_navbar">
                <div class="download">
                    <a href="###">下载APP</a>
                </div>
            </div>
        </div>
    </header>
    <script src="js/flexible.js"></script>
</body>

</html>