Because you have security plugins which block this or security settings on
server. You can use Google site kit plugin to add statistic

Could not save codes in thme options

https://prnt.sc/107uln5

such script codes:

<! - Global site tag (gtag.js) - Google Analytics ->

<script async src = "https://www.googletagmanager.com/gtag/js?id=G-TPD13WZ0X1"> </script>

<script>

   window.dataLayer = window.dataLayer || [];

   function gtag () {dataLayer.push (arguments);}

   gtag ('js', new Date ());

   gtag ('config', 'G-TPD13WZ0X1');

</script>

But you can type anything in theme options in these fields, but script codes cannot. Are there any blockages at your place?