First of all for and given are not equivalent, they differ subtly in the scoping of their $_ variable:

use strict;
use warnings;
use 5.010;

$_ = 42;
sub f { say }

given (23) { f }
for   (23) { f }
__END__
42
23
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So given creates a new lexical $_, while for localizes the existing $_, which results in dynamic scoping.

But the real reason is that code must be readable to humans, and for has the connotation of a loop, whereas given makes it implicit that it's one value that is talked about. So it's all about intent.