The reason is security. It isn't much of a problem on a laptop only you use (since then your home directory is likely none safer), but on a shared machine, or at least a shared file system, other accounts can access stuff in /tmp just fine, e.g. by replacing the file with a symlink. To perform a delete operation on a file, you only need execute permissions on the containing directory (iirc), but nothing on the file itself.

Most "terminals" just use libvte, which, true, doesn't support most control commands, including OSC 52[1].

However, xterm supports it, alacritty supports it, hterm and many others...

A stock Chromebook[2] supports OSC 52, and practically every Linux distro has options. For OSX, I know iTerm supports it if you enable the clipboard integration toggle under preferences.

A bigger issue here, though, is a recent discussion about removing support for control sequences, in general[3] for many terminals that use libvte. Some view them as a vulnerability, but others view them as a feature.[4]

[1] https://bugzilla.gnome.org/show_bug.cgi?id=795774

[2] https://chromium.googlesource.com/apps/libapps/+/master/nass...

[3] http://seclists.org/oss-sec/2017/q2/197

[4] http://seclists.org/oss-sec/2018/q2/31