It is there so your avatar won't die. Which is hilarious since they have 30 seconds recast on same, and 0 seconds on different, and you have 17 summons to pick among.
Do however notice that wyverns and puppets do not get -enmity, because they only have 20 min recasts.
Oh SE, how I love you.
Wyverns don't function like other pets, where enmity isn't a problem due to their purely supplemental damage.
By the time puppets rolled around, SE finally caught wind that lowering pet enmity is generally a bad idea, looking at YYR.
BST pets are the only wrench in the cog. But that's more of a blessing because it would thoroughly **** with BST solo if any of their AF had Pet: -Enmity.