Is there any reasoning to not always use parentheses instead?

Yes, clarity and readability.

While I certainly do not endorse memorising the precedence table, I feel non-casual programmers should know the precedence of very commonly used operators. To illustrate, if you follow the "always use parentheses" rule, you'd be obliged to write:

( my $x ) = ( $y + 42 );
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which I feel is borderline obscene. This is surely more clearly written, without the clutter of parentheses, simply as:

my $x = $y + 42;
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BTW, I would similarly object to parentheses here in C or in any language where assignment is an operator.

In Perl, I place the ultra low precedence and and or operators in the same category as the = operator, at least for non-novice Perl programmers. Being very low precedence makes them especially well-suited to flow of control, and I agree with Conway that reserving them exclusively for that purpose, for example:

open(my $fh, '<', $file) or die "error opening '$file': $!";
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or:

$meaning == 42 or next;
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is idiomatic Perl and makes the code clearer and more enjoyable to read.