[gnabgib]

In some cases (luck of the data, but often when encoding ASCII without padding) you won't see the non alphanumeric characters (62nd and 63rd place) in Base64 either. So you can't always tell the difference between Base64, Base64Url, Xxencode, or B64.

"Hello, world!" = `SGVsbG8sIHdvcmxkIQ` (base64, base64url), `BG4JgP4wg65RjQalY6E` (Xxencode), or `G4JgP4wg65RjQalY6E` (b64). A legitimate reason for choosing B64 over Base64 would be: it maintains ASCII sort-order.

Any language that has to deal with HTTP (or MIME) has to encode/decode Base64 in order to support some headers (eg Basic auth) and features (binary data from a form submission). There is no similar HTTP need for Base32, so perhaps it's less surprising it's not in the standard library?