I just read perldoc perlfunc on binmode:

 In other words: regardless of platform, use binmode() on binary data,
+ like for example images.
[download]

Since binary data is the exception (most perl scripts use strings I guess), this would be sensible and -C could then be made default on utf8 machines. But the downside is, nobody expects the mangling of binary files as default (and the spanish inquisition).